640987694 has 4 divisors (see below), whose sum is σ = 961481544. Its totient is φ = 320493846.

The previous prime is 640987693. The next prime is 640987729. The reversal of 640987694 is 496789046.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640987691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160246922 + ... + 160246925.

It is an arithmetic number, because the mean of its divisors is an integer number (240370386).

Almost surely, 2^640987694 is an apocalyptic number.

640987694 is a deficient number, since it is larger than the sum of its proper divisors (320493850).

640987694 is a wasteful number, since it uses less digits than its factorization.

640987694 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320493849.

The product of its (nonzero) digits is 2612736, while the sum is 53.

The square root of 640987694 is about 25317.7347722896. The cubic root of 640987694 is about 862.2169652836.

The spelling of 640987694 in words is "six hundred forty million, nine hundred eighty-seven thousand, six hundred ninety-four".