20816621 has 6 divisors (see below), whose sum is σ = 24215310. Its totient is φ = 17842776.

The previous prime is 20816617. The next prime is 20816623. The reversal of 20816621 is 12661802.

It can be written as a sum of positive squares in only one way, i.e., 17056900 + 3759721 = 4130^2 + 1939^2 .

It is not a de Polignac number, because 20816621 - 2² = 20816617 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20816623) 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, 212366 + ... + 212463.

It is an arithmetic number, because the mean of its divisors is an integer number (4035885).

Almost surely, 2^20816621 is an apocalyptic number.

It is an amenable number.

20816621 is a deficient number, since it is larger than the sum of its proper divisors (3398689).

20816621 is an equidigital number, since it uses as much as digits as its factorization.

20816621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 424843 (or 424836 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 20816621 is about 4562.5235341859. The cubic root of 20816621 is about 275.0870071797.

The spelling of 20816621 in words is "twenty million, eight hundred sixteen thousand, six hundred twenty-one".