20639215 has 4 divisors (see below), whose sum is σ = 24767064. Its totient is φ = 16511368.

The previous prime is 20639197. The next prime is 20639219. The reversal of 20639215 is 51293602.

20639215 = 1166² + 1167² + ... + 1180².

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 20639215 - 2²¹ = 18542063 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20639219) 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, 2063917 + ... + 2063926.

It is an arithmetic number, because the mean of its divisors is an integer number (6191766).

Almost surely, 2^20639215 is an apocalyptic number.

20639215 is a deficient number, since it is larger than the sum of its proper divisors (4127849).

20639215 is an equidigital number, since it uses as much as digits as its factorization.

20639215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4127848.

The product of its (nonzero) digits is 3240, while the sum is 28.

The square root of 20639215 is about 4543.0402815736. The cubic root of 20639215 is about 274.3033164056.

The spelling of 20639215 in words is "twenty million, six hundred thirty-nine thousand, two hundred fifteen".