20639217 has 12 divisors (see below), whose sum is σ = 27922704. Its totient is φ = 13560480.

The previous prime is 20639197. The next prime is 20639219. The reversal of 20639217 is 71293602.

It is a de Polignac number, because none of the positive numbers 2^k-20639217 is a prime.

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 11 ways as a sum of consecutive naturals, for example, 15342 + ... + 16632.

It is an arithmetic number, because the mean of its divisors is an integer number (2326892).

Almost surely, 2^20639217 is an apocalyptic number.

It is an amenable number.

20639217 is a deficient number, since it is larger than the sum of its proper divisors (7283487).

20639217 is an equidigital number, since it uses as much as digits as its factorization.

20639217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1440 (or 1367 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 30.

The square root of 20639217 is about 4543.0405016905. The cubic root of 20639217 is about 274.3033252659.

The spelling of 20639217 in words is "twenty million, six hundred thirty-nine thousand, two hundred seventeen".