664557836021 has 8 divisors (see below), whose sum is σ = 727913248920. Its totient is φ = 603898398208.

The previous prime is 664557836017. The next prime is 664557836023. The reversal of 664557836021 is 120638755466.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 95719078225 + 568838757796 = 309385^2 + 754214^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 664557836021 - 2² = 664557836017 is a prime.

It is a super-2 number, since 2×664557836021² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664557836023) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 673993256 + ... + 673994241.

It is an arithmetic number, because the mean of its divisors is an integer number (90989156115).

Almost surely, 2^664557836021 is an apocalyptic number.

It is an amenable number.

664557836021 is a deficient number, since it is larger than the sum of its proper divisors (63355412899).

664557836021 is a wasteful number, since it uses less digits than its factorization.

664557836021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1347987543.

The product of its (nonzero) digits is 7257600, while the sum is 53.

The spelling of 664557836021 in words is "six hundred sixty-four billion, five hundred fifty-seven million, eight hundred thirty-six thousand, twenty-one".