640973591 has 8 divisors (see below), whose sum is σ = 669241440. Its totient is φ = 612739072.

The previous prime is 640973579. The next prime is 640973603. The reversal of 640973591 is 195379046.

It is an interprime number because it is at equal distance from previous prime (640973579) and next prime (640973603).

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 640973591 - 2⁶ = 640973527 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640973561) 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, 36071 + ... + 50823.

It is an arithmetic number, because the mean of its divisors is an integer number (83655180).

Almost surely, 2^640973591 is an apocalyptic number.

640973591 is a deficient number, since it is larger than the sum of its proper divisors (28267849).

640973591 is a wasteful number, since it uses less digits than its factorization.

640973591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16665.

The product of its (nonzero) digits is 204120, while the sum is 44.

The square root of 640973591 is about 25317.4562505794. The cubic root of 640973591 is about 862.2106417431.

The spelling of 640973591 in words is "six hundred forty million, nine hundred seventy-three thousand, five hundred ninety-one".