20756521 has 2 divisors, whose sum is σ = 20756522. Its totient is φ = 20756520.

The previous prime is 20756509. The next prime is 20756579. The reversal of 20756521 is 12565702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19456921 + 1299600 = 4411^2 + 1140^2 .

It is a cyclic number.

It is not a de Polignac number, because 20756521 - 2⁹ = 20756009 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20756521.

It is not a weakly prime, because it can be changed into another prime (20756591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10378260 + 10378261.

It is an arithmetic number, because the mean of its divisors is an integer number (10378261).

Almost surely, 2^20756521 is an apocalyptic number.

It is an amenable number.

20756521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20756521 is an equidigital number, since it uses as much as digits as its factorization.

20756521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 20756521 is about 4555.9325060848. The cubic root of 20756521 is about 274.8220159604.

The spelling of 20756521 in words is "twenty million, seven hundred fifty-six thousand, five hundred twenty-one".