20551621 has 2 divisors, whose sum is σ = 20551622. Its totient is φ = 20551620.

The previous prime is 20551607. The next prime is 20551637. The reversal of 20551621 is 12615502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20349121 + 202500 = 4511^2 + 450^2 .

It is a cyclic number.

It is not a de Polignac number, because 20551621 - 2⁷ = 20551493 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20551592 and 20551601.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20558621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10275810 + 10275811.

It is an arithmetic number, because the mean of its divisors is an integer number (10275811).

Almost surely, 2^20551621 is an apocalyptic number.

It is an amenable number.

20551621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20551621 is an equidigital number, since it uses as much as digits as its factorization.

20551621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 600, while the sum is 22.

The square root of 20551621 is about 4533.3895707296. The cubic root of 20551621 is about 273.9147131863.

The spelling of 20551621 in words is "twenty million, five hundred fifty-one thousand, six hundred twenty-one".