647665531 has 4 divisors (see below), whose sum is σ = 647881000. Its totient is φ = 647450064.

The previous prime is 647665519. The next prime is 647665537. The reversal of 647665531 is 135566746.

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 647665531 - 2¹¹ = 647663483 is a prime.

It is a super-2 number, since 2×647665531² = 838941280091023922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (647665537) 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, 103161 + ... + 109258.

It is an arithmetic number, because the mean of its divisors is an integer number (161970250).

Almost surely, 2^647665531 is an apocalyptic number.

647665531 is a deficient number, since it is larger than the sum of its proper divisors (215469).

647665531 is a wasteful number, since it uses less digits than its factorization.

647665531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215468.

The product of its digits is 453600, while the sum is 43.

The square root of 647665531 is about 25449.2736831525. The cubic root of 647665531 is about 865.2008314465.

The spelling of 647665531 in words is "six hundred forty-seven million, six hundred sixty-five thousand, five hundred thirty-one".