20756621 has 2 divisors, whose sum is σ = 20756622. Its totient is φ = 20756620.

The previous prime is 20756599. The next prime is 20756623. The reversal of 20756621 is 12665702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17556100 + 3200521 = 4190^2 + 1789^2 .

It is a cyclic number.

It is not a de Polignac number, because 20756621 - 2¹⁰ = 20755597 is a prime.

Together with 20756623, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20756623) 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 as a sum of consecutive naturals, namely, 10378310 + 10378311.

It is an arithmetic number, because the mean of its divisors is an integer number (10378311).

Almost surely, 2^20756621 is an apocalyptic number.

It is an amenable number.

20756621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20756621 is an equidigital number, since it uses as much as digits as its factorization.

20756621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5040, while the sum is 29.

The square root of 20756621 is about 4555.9434807732. The cubic root of 20756621 is about 274.8224573022.

The spelling of 20756621 in words is "twenty million, seven hundred fifty-six thousand, six hundred twenty-one".