66291639 has 4 divisors (see below), whose sum is σ = 88388856. Its totient is φ = 44194424.

The previous prime is 66291637. The next prime is 66291647. The reversal of 66291639 is 93619266.

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 66291639 - 2¹ = 66291637 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66291639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66291637) 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, 11048604 + ... + 11048609.

It is an arithmetic number, because the mean of its divisors is an integer number (22097214).

Almost surely, 2^66291639 is an apocalyptic number.

66291639 is a deficient number, since it is larger than the sum of its proper divisors (22097217).

66291639 is a wasteful number, since it uses less digits than its factorization.

66291639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22097216.

The product of its digits is 104976, while the sum is 42.

The square root of 66291639 is about 8141.9677597004. The cubic root of 66291639 is about 404.7183714984.

The spelling of 66291639 in words is "sixty-six million, two hundred ninety-one thousand, six hundred thirty-nine".