20621621 has 4 divisors (see below), whose sum is σ = 20971200. Its totient is φ = 20272044.

The previous prime is 20621609. The next prime is 20621677. The reversal of 20621621 is 12612602.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20621621 - 2¹⁰ = 20620597 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20621593 and 20621602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20621921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 174701 + ... + 174818.

It is an arithmetic number, because the mean of its divisors is an integer number (5242800).

Almost surely, 2^20621621 is an apocalyptic number.

It is an amenable number.

20621621 is a deficient number, since it is larger than the sum of its proper divisors (349579).

20621621 is an equidigital number, since it uses as much as digits as its factorization.

20621621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 349578.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 20621621 is about 4541.1035002519. The cubic root of 20621621 is about 274.2253505117.

The spelling of 20621621 in words is "twenty million, six hundred twenty-one thousand, six hundred twenty-one".