66139509 has 4 divisors (see below), whose sum is σ = 88186016. Its totient is φ = 44093004.

The previous prime is 66139499. The next prime is 66139529. The reversal of 66139509 is 90593166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 66139509 - 2⁵ = 66139477 is a prime.

It is a super-2 number, since 2×66139509² = 8748869301522162, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66139529) 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, 11023249 + ... + 11023254.

It is an arithmetic number, because the mean of its divisors is an integer number (22046504).

Almost surely, 2^66139509 is an apocalyptic number.

It is an amenable number.

66139509 is a deficient number, since it is larger than the sum of its proper divisors (22046507).

66139509 is a wasteful number, since it uses less digits than its factorization.

66139509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22046506.

The product of its (nonzero) digits is 43740, while the sum is 39.

The square root of 66139509 is about 8132.6200575214. The cubic root of 66139509 is about 404.4085437688.

The spelling of 66139509 in words is "sixty-six million, one hundred thirty-nine thousand, five hundred nine".