100400020 has 72 divisors (see below), whose sum is σ = 250019784. Its totient is φ = 33755904.

The previous prime is 100400017. The next prime is 100400023. The reversal of 100400020 is 20004001.

It is an interprime number because it is at equal distance from previous prime (100400017) and next prime (100400023).

It can be written as a sum of positive squares in 4 ways, for example, as 25542916 + 74857104 = 5054^2 + 8652^2 .

It is a Harshad number since it is a multiple of its sum of digits (7).

It is a junction number, because it is equal to n+sod(n) for n = 100399976 and 100400012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (100400023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 50974 + ... + 52906.

It is an arithmetic number, because the mean of its divisors is an integer number (3472497).

Almost surely, 2^100400020 is an apocalyptic number.

100400020 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 100400020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (125009892).

100400020 is an abundant number, since it is smaller than the sum of its proper divisors (149619764).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

100400020 is a wasteful number, since it uses less digits than its factorization.

100400020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2009 (or 2000 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 7.

The square root of 100400020 is about 10019.9810379062. The cubic root of 100400020 is about 464.7769693916.

Adding to 100400020 its reverse (20004001), we get a palindrome (120404021).

The spelling of 100400020 in words is "one hundred million, four hundred thousand, twenty".