647640731 has 4 divisors (see below), whose sum is σ = 669973200. Its totient is φ = 625308264.

The previous prime is 647640727. The next prime is 647640751. The reversal of 647640731 is 137046746.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 137046746 = 2 ⋅68523373.

It is a cyclic number.

It is not a de Polignac number, because 647640731 - 2² = 647640727 is a prime.

It is a super-2 number, since 2×647640731² = 838877032900428722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (647640701) 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, 11166191 + ... + 11166248.

It is an arithmetic number, because the mean of its divisors is an integer number (167493300).

Almost surely, 2^647640731 is an apocalyptic number.

647640731 is a deficient number, since it is larger than the sum of its proper divisors (22332469).

647640731 is a wasteful number, since it uses less digits than its factorization.

647640731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22332468.

The product of its (nonzero) digits is 84672, while the sum is 38.

The square root of 647640731 is about 25448.7864347202. The cubic root of 647640731 is about 865.1897880640.

The spelling of 647640731 in words is "six hundred forty-seven million, six hundred forty thousand, seven hundred thirty-one".