21135208668 has 48 divisors (see below), whose sum is σ = 58811020800. Its totient is φ = 5776081344.

The previous prime is 21135208667. The next prime is 21135208687. The reversal of 21135208668 is 86680253112.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135208667) 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, 5467843 + ... + 5471706.

It is an arithmetic number, because the mean of its divisors is an integer number (1225229600).

Almost surely, 2^21135208668 is an apocalyptic number.

21135208668 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21135208668 is an abundant number, since it is smaller than the sum of its proper divisors (37675812132).

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

21135208668 is a wasteful number, since it uses less digits than its factorization.

21135208668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10939586 (or 10939584 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 42.

The spelling of 21135208668 in words is "twenty-one billion, one hundred thirty-five million, two hundred eight thousand, six hundred sixty-eight".