20808621 has 6 divisors (see below), whose sum is σ = 30056910. Its totient is φ = 13872408.

The previous prime is 20808617. The next prime is 20808637. The reversal of 20808621 is 12680802.

It can be written as a sum of positive squares in only one way, i.e., 15920100 + 4888521 = 3990^2 + 2211^2 .

It is not a de Polignac number, because 20808621 - 2² = 20808617 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20808691) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1156026 + ... + 1156043.

It is an arithmetic number, because the mean of its divisors is an integer number (5009485).

Almost surely, 2^20808621 is an apocalyptic number.

It is an amenable number.

20808621 is a deficient number, since it is larger than the sum of its proper divisors (9248289).

20808621 is a wasteful number, since it uses less digits than its factorization.

20808621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2312075 (or 2312072 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 20808621 is about 4561.6467421316. The cubic root of 20808621 is about 275.0517632587.

It can be divided in two parts, 2080 and 8621, that added together give a palindrome (10701).

The spelling of 20808621 in words is "twenty million, eight hundred eight thousand, six hundred twenty-one".