66139791 has 4 divisors (see below), whose sum is σ = 88186392. Its totient is φ = 44093192.

The previous prime is 66139781. The next prime is 66139823. The reversal of 66139791 is 19793166.

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 66139791 - 2⁷ = 66139663 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66139781) 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, 11023296 + ... + 11023301.

It is an arithmetic number, because the mean of its divisors is an integer number (22046598).

Almost surely, 2^66139791 is an apocalyptic number.

66139791 is a deficient number, since it is larger than the sum of its proper divisors (22046601).

66139791 is a wasteful number, since it uses less digits than its factorization.

66139791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22046600.

The product of its digits is 61236, while the sum is 42.

The square root of 66139791 is about 8132.6373950890. The cubic root of 66139791 is about 404.4091185289.

The spelling of 66139791 in words is "sixty-six million, one hundred thirty-nine thousand, seven hundred ninety-one".