640607761 has 4 divisors (see below), whose sum is σ = 648716800. Its totient is φ = 632498724.

The previous prime is 640607749. The next prime is 640607797. The reversal of 640607761 is 167706046.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 640607761 - 2⁷ = 640607633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 640607761.

It is not an unprimeable number, because it can be changed into a prime (640607701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4054401 + ... + 4054558.

It is an arithmetic number, because the mean of its divisors is an integer number (162179200).

Almost surely, 2^640607761 is an apocalyptic number.

It is an amenable number.

640607761 is a deficient number, since it is larger than the sum of its proper divisors (8109039).

640607761 is an equidigital number, since it uses as much as digits as its factorization.

640607761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8109038.

The product of its (nonzero) digits is 42336, while the sum is 37.

The square root of 640607761 is about 25310.2303624444. The cubic root of 640607761 is about 862.0465774973.

The spelling of 640607761 in words is "six hundred forty million, six hundred seven thousand, seven hundred sixty-one".