640661457 has 8 divisors (see below), whose sum is σ = 860450976. Its totient is φ = 423989792.

The previous prime is 640661453. The next prime is 640661459. The reversal of 640661457 is 754166046.

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

It is not a de Polignac number, because 640661457 - 2² = 640661453 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640661453) 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, 778983 + ... + 779804.

It is an arithmetic number, because the mean of its divisors is an integer number (107556372).

Almost surely, 2^640661457 is an apocalyptic number.

It is an amenable number.

640661457 is a deficient number, since it is larger than the sum of its proper divisors (219789519).

640661457 is a wasteful number, since it uses less digits than its factorization.

640661457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1558927.

The product of its (nonzero) digits is 120960, while the sum is 39.

The square root of 640661457 is about 25311.2910970579. The cubic root of 640661457 is about 862.0706625212.

The spelling of 640661457 in words is "six hundred forty million, six hundred sixty-one thousand, four hundred fifty-seven".