21400020 has 72 divisors (see below), whose sum is σ = 66011400. Its totient is φ = 5610240.

The previous prime is 21400003. The next prime is 21400031. The reversal of 21400020 is 2000412.

It can be written as a sum of positive squares in 4 ways, for example, as 715716 + 20684304 = 846^2 + 4548^2 .

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21399975 and 21400011.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10006 + ... + 11954.

It is an arithmetic number, because the mean of its divisors is an integer number (916825).

Almost surely, 2^21400020 is an apocalyptic number.

21400020 is a gapful number since it is divisible by the number (20) 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 21400020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33005700).

21400020 is an abundant number, since it is smaller than the sum of its proper divisors (44611380).

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

21400020 is a wasteful number, since it uses less digits than its factorization.

21400020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2025 (or 2020 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

The square root of 21400020 is about 4626.0155641762. The cubic root of 21400020 is about 277.6331963446.

Adding to 21400020 its reverse (2000412), we get a palindrome (23400432).

The spelling of 21400020 in words is "twenty-one million, four hundred thousand, twenty".