21011665600 has 42 divisors (see below), whose sum is σ = 51701833604. Its totient is φ = 8404665600.

The previous prime is 21011665501. The next prime is 21011665621. The reversal of 21011665600 is 656611012.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6564546 + ... + 6567745.

Almost surely, 2^21011665600 is an apocalyptic number.

21011665600 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21011665600 is an abundant number, since it is smaller than the sum of its proper divisors (30690168004).

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

21011665600 is a wasteful number, since it uses less digits than its factorization.

21011665600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13132313 (or 13132298 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 28.

The spelling of 21011665600 in words is "twenty-one billion, eleven million, six hundred sixty-five thousand, six hundred".