66991131 has 60 divisors (see below), whose sum is σ = 110642400. Its totient is φ = 40334112.

The previous prime is 66991117. The next prime is 66991163. The reversal of 66991131 is 13119966.

It is not a de Polignac number, because 66991131 - 2²⁵ = 33436699 is a prime.

It is a super-2 number, since 2×66991131² = 8975623265318322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (66991231) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 847950 + ... + 848028.

It is an arithmetic number, because the mean of its divisors is an integer number (1844040).

Almost surely, 2^66991131 is an apocalyptic number.

66991131 is a deficient number, since it is larger than the sum of its proper divisors (43651269).

66991131 is a wasteful number, since it uses less digits than its factorization.

66991131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158 (or 130 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 66991131 is about 8184.8109935416. The cubic root of 66991131 is about 406.1368879253.

The spelling of 66991131 in words is "sixty-six million, nine hundred ninety-one thousand, one hundred thirty-one".