66815131 has 4 divisors (see below), whose sum is σ = 66875752. Its totient is φ = 66754512.

The previous prime is 66815113. The next prime is 66815143. The reversal of 66815131 is 13151866.

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 66815131 - 2⁹ = 66814619 is a prime.

It is a super-2 number, since 2×66815131² = 8928523461094322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 66815093 and 66815102.

It is not an unprimeable number, because it can be changed into a prime (66815731) 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, 28626 + ... + 30871.

It is an arithmetic number, because the mean of its divisors is an integer number (16718938).

Almost surely, 2^66815131 is an apocalyptic number.

66815131 is a deficient number, since it is larger than the sum of its proper divisors (60621).

66815131 is a wasteful number, since it uses less digits than its factorization.

66815131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60620.

The product of its digits is 4320, while the sum is 31.

The square root of 66815131 is about 8174.0522998082. The cubic root of 66815131 is about 405.7809065660.

Adding to 66815131 its reverse (13151866), we get a palindrome (79966997).

The spelling of 66815131 in words is "sixty-six million, eight hundred fifteen thousand, one hundred thirty-one".