640621663 has 8 divisors (see below), whose sum is σ = 717748560. Its totient is φ = 566642880.

The previous prime is 640621649. The next prime is 640621669. The reversal of 640621663 is 366126046.

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 640621663 - 2²¹ = 638524511 is a prime.

It is a super-2 number, since 2×640621663² = 820792230209771138, which 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 (640621669) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 786598 + ... + 787411.

It is an arithmetic number, because the mean of its divisors is an integer number (89718570).

Almost surely, 2^640621663 is an apocalyptic number.

640621663 is a deficient number, since it is larger than the sum of its proper divisors (77126897).

640621663 is a wasteful number, since it uses less digits than its factorization.

640621663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1574057.

The product of its (nonzero) digits is 31104, while the sum is 34.

The square root of 640621663 is about 25310.5049929866. The cubic root of 640621663 is about 862.0528132865.

The spelling of 640621663 in words is "six hundred forty million, six hundred twenty-one thousand, six hundred sixty-three".