21515662668 has 12 divisors (see below), whose sum is σ = 50203212920. Its totient is φ = 7171887552.

The previous prime is 21515662657. The next prime is 21515662697. The reversal of 21515662668 is 86626651512.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-3 number, since 3×21515662668³ (a number of 32 digits) contains 333 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 896485933 + ... + 896485956.

Almost surely, 2^21515662668 is an apocalyptic number.

It is an amenable number.

21515662668 is an abundant number, since it is smaller than the sum of its proper divisors (28687550252).

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

21515662668 is a wasteful number, since it uses less digits than its factorization.

21515662668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1792971896 (or 1792971894 counting only the distinct ones).

The product of its digits is 1036800, while the sum is 48.

The spelling of 21515662668 in words is "twenty-one billion, five hundred fifteen million, six hundred sixty-two thousand, six hundred sixty-eight".