21000021012 has 48 divisors (see below), whose sum is σ = 54479335680. Its totient is φ = 6995528064.

The previous prime is 21000020999. The next prime is 21000021019. The reversal of 21000021012 is 21012000012.

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 = 21000020985 and 21000021003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000021019) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 109548 + ... + 232380.

It is an arithmetic number, because the mean of its divisors is an integer number (1134986160).

Almost surely, 2^21000021012 is an apocalyptic number.

It is an amenable number.

21000021012 is an abundant number, since it is smaller than the sum of its proper divisors (33479314668).

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

21000021012 is a wasteful number, since it uses less digits than its factorization.

21000021012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124429 (or 124421 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21000021012 its reverse (21012000012), we get a palindrome (42012021024).

The spelling of 21000021012 in words is "twenty-one billion, twenty-one thousand, twelve".