21507700665 has 64 divisors (see below), whose sum is σ = 38531469312. Its totient is φ = 10153766400.

The previous prime is 21507700657. The next prime is 21507700667. The reversal of 21507700665 is 56600770512.

It is not a de Polignac number, because 21507700665 - 2³ = 21507700657 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21507700667) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3805872 + ... + 3811518.

It is an arithmetic number, because the mean of its divisors is an integer number (602054208).

Almost surely, 2^21507700665 is an apocalyptic number.

It is an amenable number.

21507700665 is a deficient number, since it is larger than the sum of its proper divisors (17023768647).

21507700665 is a wasteful number, since it uses less digits than its factorization.

21507700665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6270.

The product of its (nonzero) digits is 88200, while the sum is 39.

The spelling of 21507700665 in words is "twenty-one billion, five hundred seven million, seven hundred thousand, six hundred sixty-five".