20556621 has 48 divisors (see below), whose sum is σ = 33611760. Its totient is φ = 12042240.

The previous prime is 20556619. The next prime is 20556647. The reversal of 20556621 is 12665502.

It can be written as a sum of positive squares in 8 ways, for example, as 3861225 + 16695396 = 1965^2 + 4086^2 .

It is not a de Polignac number, because 20556621 - 2¹ = 20556619 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20556671) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 181861 + ... + 181973.

It is an arithmetic number, because the mean of its divisors is an integer number (700245).

Almost surely, 2^20556621 is an apocalyptic number.

It is an amenable number.

20556621 is a deficient number, since it is larger than the sum of its proper divisors (13055139).

20556621 is a wasteful number, since it uses less digits than its factorization.

20556621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 203 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 20556621 is about 4533.9410009395. The cubic root of 20556621 is about 273.9369249381.

The spelling of 20556621 in words is "twenty million, five hundred fifty-six thousand, six hundred twenty-one".