66817531 has 16 divisors (see below), whose sum is σ = 77843808. Its totient is φ = 57150720.

The previous prime is 66817519. The next prime is 66817589. The reversal of 66817531 is 13571866.

It is not a de Polignac number, because 66817531 - 2¹⁹ = 66293243 is a prime.

It is a super-2 number, since 2×66817531² = 8929164897871922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66817591) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21151 + ... + 24103.

It is an arithmetic number, because the mean of its divisors is an integer number (4865238).

Almost surely, 2^66817531 is an apocalyptic number.

66817531 is a deficient number, since it is larger than the sum of its proper divisors (11026277).

66817531 is a wasteful number, since it uses less digits than its factorization.

66817531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3003 (or 2981 counting only the distinct ones).

The product of its digits is 30240, while the sum is 37.

The square root of 66817531 is about 8174.1991044995. The cubic root of 66817531 is about 405.7857650589.

The spelling of 66817531 in words is "sixty-six million, eight hundred seventeen thousand, five hundred thirty-one".