20639971 has 8 divisors (see below), whose sum is σ = 22680000. Its totient is φ = 18627240.

The previous prime is 20639959. The next prime is 20640001. The reversal of 20639971 is 17993602.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20639971 - 2⁵ = 20639939 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20639971.

It is not an unprimeable number, because it can be changed into a prime (20639471) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5221 + ... + 8278.

It is an arithmetic number, because the mean of its divisors is an integer number (2835000).

Almost surely, 2^20639971 is an apocalyptic number.

20639971 is a deficient number, since it is larger than the sum of its proper divisors (2040029).

20639971 is a wasteful number, since it uses less digits than its factorization.

20639971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13649.

The product of its (nonzero) digits is 20412, while the sum is 37.

The square root of 20639971 is about 4543.1234850046. The cubic root of 20639971 is about 274.3066655442.

The spelling of 20639971 in words is "twenty million, six hundred thirty-nine thousand, nine hundred seventy-one".