21100020 has 24 divisors (see below), whose sum is σ = 59080224. Its totient is φ = 5626656.

The previous prime is 21100019. The next prime is 21100021. The reversal of 21100020 is 2000112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21100019) and next prime (21100021).

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a junction number, because it is equal to n+sod(n) for n = 21099981 and 21100008.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175774 + ... + 175893.

It is an arithmetic number, because the mean of its divisors is an integer number (2461676).

Almost surely, 2^21100020 is an apocalyptic number.

21100020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21100020 is an abundant number, since it is smaller than the sum of its proper divisors (37980204).

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

21100020 is a wasteful number, since it uses less digits than its factorization.

21100020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 351679 (or 351677 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 21100020 is about 4593.4758081435. The cubic root of 21100020 is about 276.3297361334.

Adding to 21100020 its reverse (2000112), we get a palindrome (23100132).

The spelling of 21100020 in words is "twenty-one million, one hundred thousand, twenty".