21020100 has 36 divisors (see below), whose sum is σ = 60819024. Its totient is φ = 5605280.

The previous prime is 21020093. The next prime is 21020117. The reversal of 21020100 is 102012.

It is a happy number.

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 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 11 ways as a sum of consecutive naturals, for example, 34734 + ... + 35333.

Almost surely, 2^21020100 is an apocalyptic number.

21020100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21020100 is an abundant number, since it is smaller than the sum of its proper divisors (39798924).

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

21020100 is a wasteful number, since it uses less digits than its factorization.

21020100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70084 (or 70077 counting only the distinct ones).

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

The square root of 21020100 is about 4584.7682602286. The cubic root of 21020100 is about 275.9804123885.

Adding to 21020100 its reverse (102012), we get a palindrome (21122112).

The spelling of 21020100 in words is "twenty-one million, twenty thousand, one hundred".