639636379 has 4 divisors (see below), whose sum is σ = 640271320. Its totient is φ = 639001440.

The previous prime is 639636343. The next prime is 639636391. The reversal of 639636379 is 973636936.

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

It is a cyclic number.

It is not a de Polignac number, because 639636379 - 2¹⁵ = 639603611 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639636329) 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, 315957 + ... + 317974.

It is an arithmetic number, because the mean of its divisors is an integer number (160067830).

Almost surely, 2^639636379 is an apocalyptic number.

639636379 is a deficient number, since it is larger than the sum of its proper divisors (634941).

639636379 is a wasteful number, since it uses less digits than its factorization.

639636379 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 634940.

The product of its digits is 3306744, while the sum is 52.

The square root of 639636379 is about 25291.0335692316. The cubic root of 639636379 is about 861.6106372403.

The spelling of 639636379 in words is "six hundred thirty-nine million, six hundred thirty-six thousand, three hundred seventy-nine".