640889794 has 4 divisors (see below), whose sum is σ = 961334694. Its totient is φ = 320444896.

The previous prime is 640889761. The next prime is 640889803. The reversal of 640889794 is 497988046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 497988046 = 2 ⋅248994023.

It can be written as a sum of positive squares in only one way, i.e., 468939025 + 171950769 = 21655^2 + 13113^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160222447 + ... + 160222450.

Almost surely, 2^640889794 is an apocalyptic number.

640889794 is a deficient number, since it is larger than the sum of its proper divisors (320444900).

640889794 is a wasteful number, since it uses less digits than its factorization.

640889794 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320444899.

The product of its (nonzero) digits is 3483648, while the sum is 55.

The square root of 640889794 is about 25315.8012711429. The cubic root of 640889794 is about 862.1730667088.

The spelling of 640889794 in words is "six hundred forty million, eight hundred eighty-nine thousand, seven hundred ninety-four".