20562721 has 2 divisors, whose sum is σ = 20562722. Its totient is φ = 20562720.

The previous prime is 20562719. The next prime is 20562733. The reversal of 20562721 is 12726502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15563025 + 4999696 = 3945^2 + 2236^2 .

It is a cyclic number.

It is not a de Polignac number, because 20562721 - 2¹ = 20562719 is a prime.

Together with 20562719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20562221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10281360 + 10281361.

It is an arithmetic number, because the mean of its divisors is an integer number (10281361).

Almost surely, 2^20562721 is an apocalyptic number.

It is an amenable number.

20562721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20562721 is an equidigital number, since it uses as much as digits as its factorization.

20562721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 20562721 is about 4534.6136549876. The cubic root of 20562721 is about 273.9640183983.

It can be divided in two parts, 205 and 62721, that added together give a palindrome (62926).

The spelling of 20562721 in words is "twenty million, five hundred sixty-two thousand, seven hundred twenty-one".