21622621 has 4 divisors (see below), whose sum is σ = 22150044. Its totient is φ = 21095200.

The previous prime is 21622613. The next prime is 21622631. The reversal of 21622621 is 12622612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1020100 + 20602521 = 1010^2 + 4539^2 .

It is a cyclic number.

It is not a de Polignac number, because 21622621 - 2³ = 21622613 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21622592 and 21622601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21622631) 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, 263650 + ... + 263731.

It is an arithmetic number, because the mean of its divisors is an integer number (5537511).

Almost surely, 2^21622621 is an apocalyptic number.

It is an amenable number.

21622621 is a deficient number, since it is larger than the sum of its proper divisors (527423).

21622621 is an equidigital number, since it uses as much as digits as its factorization.

21622621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 527422.

The product of its digits is 576, while the sum is 22.

The square root of 21622621 is about 4650.0130107345. The cubic root of 21622621 is about 278.5925158953.

Subtracting from 21622621 its reverse (12622612), we obtain a palindrome (9000009).

The spelling of 21622621 in words is "twenty-one million, six hundred twenty-two thousand, six hundred twenty-one".