639535587921 has 24 divisors (see below), whose sum is σ = 966019781376. Its totient is φ = 406938913920.

The previous prime is 639535587913. The next prime is 639535587979. The reversal of 639535587921 is 129785535936.

It is a happy number.

639535587921 is a `hidden beast` number, since 6 + 3 + 9 + 5 + 3 + 558 + 79 + 2 + 1 = 666.

It is not a de Polignac number, because 639535587921 - 2³ = 639535587913 is a prime.

It is a super-3 number, since 3×639535587921³ (a number of 36 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (639535587721) 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, 3240600 + ... + 3432281.

It is an arithmetic number, because the mean of its divisors is an integer number (40250824224).

Almost surely, 2^639535587921 is an apocalyptic number.

It is an amenable number.

639535587921 is a deficient number, since it is larger than the sum of its proper divisors (326484193455).

639535587921 is a wasteful number, since it uses less digits than its factorization.

639535587921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6673373 (or 6673370 counting only the distinct ones).

The product of its digits is 61236000, while the sum is 63.

The spelling of 639535587921 in words is "six hundred thirty-nine billion, five hundred thirty-five million, five hundred eighty-seven thousand, nine hundred twenty-one".