21000012100 has 36 divisors (see below), whose sum is σ = 45578711248. Its totient is φ = 8398404000.

The previous prime is 21000012083. The next prime is 21000012107. The reversal of 21000012100 is 121000012.

It is not an unprimeable number, because it can be changed into a prime (21000012107) 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, 604195 + ... + 638005.

Almost surely, 2^21000012100 is an apocalyptic number.

21000012100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000012100 is an abundant number, since it is smaller than the sum of its proper divisors (24578699148).

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

21000012100 is a wasteful number, since it uses less digits than its factorization.

21000012100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40036 (or 40029 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 21000012100 its reverse (121000012), we get a palindrome (21121012112).

The spelling of 21000012100 in words is "twenty-one billion, twelve thousand, one hundred".