20513561 has 2 divisors, whose sum is σ = 20513562. Its totient is φ = 20513560.

The previous prime is 20513557. The next prime is 20513567. The reversal of 20513561 is 16531502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18966025 + 1547536 = 4355^2 + 1244^2 .

It is a cyclic number.

It is not a de Polignac number, because 20513561 - 2² = 20513557 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20513567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10256780 + 10256781.

It is an arithmetic number, because the mean of its divisors is an integer number (10256781).

Almost surely, 2^20513561 is an apocalyptic number.

It is an amenable number.

20513561 is a deficient number, since it is larger than the sum of its proper divisors (1).

20513561 is an equidigital number, since it uses as much as digits as its factorization.

20513561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 20513561 is about 4529.1898834118. The cubic root of 20513561 is about 273.7455191332.

The spelling of 20513561 in words is "twenty million, five hundred thirteen thousand, five hundred sixty-one".