21000100023 has 24 divisors (see below), whose sum is σ = 34688544800. Its totient is φ = 11992541184.

The previous prime is 21000100003. The next prime is 21000100031. The reversal of 21000100023 is 32000100012.

It is a happy number.

It is not a de Polignac number, because 21000100023 - 2⁶ = 21000099959 is a prime.

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 = 21000099978 and 21000100014.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000100003) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2218 + ... + 204951.

Almost surely, 2^21000100023 is an apocalyptic number.

21000100023 is a deficient number, since it is larger than the sum of its proper divisors (13688444777).

21000100023 is a wasteful number, since it uses less digits than its factorization.

21000100023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 208791 (or 208788 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

Adding to 21000100023 its reverse (32000100012), we get a palindrome (53000200035).

The spelling of 21000100023 in words is "twenty-one billion, one hundred thousand, twenty-three".