21640767993 has 24 divisors (see below), whose sum is σ = 33771716160. Its totient is φ = 13274552160.

The previous prime is 21640767983. The next prime is 21640768027. The reversal of 21640767993 is 39976704612.

It is a happy number.

It is not a de Polignac number, because 21640767993 - 2⁸ = 21640767737 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21640767923) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 260983 + ... + 333756.

It is an arithmetic number, because the mean of its divisors is an integer number (1407154840).

Almost surely, 2^21640767993 is an apocalyptic number.

It is an amenable number.

21640767993 is a deficient number, since it is larger than the sum of its proper divisors (12130948167).

21640767993 is a wasteful number, since it uses less digits than its factorization.

21640767993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 595069 (or 595066 counting only the distinct ones).

The product of its (nonzero) digits is 3429216, while the sum is 54.

The spelling of 21640767993 in words is "twenty-one billion, six hundred forty million, seven hundred sixty-seven thousand, nine hundred ninety-three".