639854921 has 4 divisors (see below), whose sum is σ = 654735312. Its totient is φ = 624974532.

The previous prime is 639854903. The next prime is 639854923. The reversal of 639854921 is 129458936.

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 639854921 - 2¹⁰ = 639853897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639854923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7440131 + ... + 7440216.

It is an arithmetic number, because the mean of its divisors is an integer number (163683828).

Almost surely, 2^639854921 is an apocalyptic number.

It is an amenable number.

639854921 is a deficient number, since it is larger than the sum of its proper divisors (14880391).

639854921 is a wasteful number, since it uses less digits than its factorization.

639854921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14880390.

The product of its digits is 466560, while the sum is 47.

The square root of 639854921 is about 25295.3537433261. The cubic root of 639854921 is about 861.7087537521.

The spelling of 639854921 in words is "six hundred thirty-nine million, eight hundred fifty-four thousand, nine hundred twenty-one".