639249217 has 4 divisors (see below), whose sum is σ = 639413460. Its totient is φ = 639084976.

The previous prime is 639249199. The next prime is 639249227. The reversal of 639249217 is 712942936.

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

It can be written as a sum of positive squares in 2 ways, for example, as 484396081 + 154853136 = 22009^2 + 12444^2 .

It is a cyclic number.

It is not a de Polignac number, because 639249217 - 2²³ = 630860609 is a prime.

It is a super-2 number, since 2×639249217² = 817279122870226178, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639249227) 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, 76138 + ... + 84115.

It is an arithmetic number, because the mean of its divisors is an integer number (159853365).

Almost surely, 2^639249217 is an apocalyptic number.

It is an amenable number.

639249217 is a deficient number, since it is larger than the sum of its proper divisors (164243).

639249217 is a wasteful number, since it uses less digits than its factorization.

639249217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164242.

The product of its digits is 163296, while the sum is 43.

The square root of 639249217 is about 25283.3782750644. The cubic root of 639249217 is about 861.4367622934.

The spelling of 639249217 in words is "six hundred thirty-nine million, two hundred forty-nine thousand, two hundred seventeen".