639769994 has 4 divisors (see below), whose sum is σ = 959654994. Its totient is φ = 319884996.

The previous prime is 639769987. The next prime is 639770023. The reversal of 639769994 is 499967936.

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

It can be written as a sum of positive squares in only one way, i.e., 618268225 + 21501769 = 24865^2 + 4637^2 .

It is a super-4 number, since 4×639769994⁴ (a number of 36 digits) contains 4444 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159942497 + ... + 159942500.

Almost surely, 2^639769994 is an apocalyptic number.

639769994 is a deficient number, since it is larger than the sum of its proper divisors (319885000).

639769994 is a wasteful number, since it uses less digits than its factorization.

639769994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319884999.

The product of its digits is 19840464, while the sum is 62.

The square root of 639769994 is about 25293.6749801210. The cubic root of 639769994 is about 861.6706276212.

The spelling of 639769994 in words is "six hundred thirty-nine million, seven hundred sixty-nine thousand, nine hundred ninety-four".