21021012100 has 36 divisors (see below), whose sum is σ = 49762471248. Its totient is φ = 7644004000.

The previous prime is 21021012041. The next prime is 21021012109. The reversal of 21021012100 is 121012012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is not an unprimeable number, because it can be changed into a prime (21021012109) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9553906 + ... + 9556105.

It is an arithmetic number, because the mean of its divisors is an integer number (1382290868).

Almost surely, 2^21021012100 is an apocalyptic number.

21021012100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021012100 is an abundant number, since it is smaller than the sum of its proper divisors (28741459148).

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

21021012100 is a wasteful number, since it uses less digits than its factorization.

21021012100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19110036 (or 19110029 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21021012100 its reverse (121012012), we get a palindrome (21142024112).

The spelling of 21021012100 in words is "twenty-one billion, twenty-one million, twelve thousand, one hundred".