639690 has 16 divisors (see below), whose sum is σ = 1535328. Its totient is φ = 170576.

The previous prime is 639689. The next prime is 639697. The reversal of 639690 is 96936.

It is a super-2 number, since 2×639690² = 818406592200, which contains 22 as substring.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (639697) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10632 + ... + 10691.

It is an arithmetic number, because the mean of its divisors is an integer number (95958).

2⁶³⁹⁶⁹⁰ is an apocalyptic number.

639690 is an abundant number, since it is smaller than the sum of its proper divisors (895638).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639690 is a wasteful number, since it uses less digits than its factorization.

639690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21333.

The product of its (nonzero) digits is 8748, while the sum is 33.

The square root of 639690 is about 799.8062265324. The cubic root of 639690 is about 86.1634712968.

The spelling of 639690 in words is "six hundred thirty-nine thousand, six hundred ninety".