20871621 has 8 divisors (see below), whose sum is σ = 30920960. Its totient is φ = 13914396.

The previous prime is 20871593. The next prime is 20871623. The reversal of 20871621 is 12617802.

It is not a de Polignac number, because 20871621 - 2¹¹ = 20869573 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 773023 = 20871621 / (2 + 0 + 8 + 7 + 1 + 6 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20871623) 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, 386485 + ... + 386538.

It is an arithmetic number, because the mean of its divisors is an integer number (3865120).

Almost surely, 2^20871621 is an apocalyptic number.

It is an amenable number.

20871621 is a deficient number, since it is larger than the sum of its proper divisors (10049339).

20871621 is an equidigital number, since it uses as much as digits as its factorization.

20871621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 773032 (or 773026 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 20871621 is about 4568.5469243513. The cubic root of 20871621 is about 275.3290650368.

The spelling of 20871621 in words is "twenty million, eight hundred seventy-one thousand, six hundred twenty-one".