20561137 has 4 divisors (see below), whose sum is σ = 20998656. Its totient is φ = 20123620.

The previous prime is 20561117. The next prime is 20561147. The reversal of 20561137 is 73116502.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20561137 - 2¹⁵ = 20528369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20561117) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 218689 + ... + 218782.

It is an arithmetic number, because the mean of its divisors is an integer number (5249664).

Almost surely, 2^20561137 is an apocalyptic number.

It is an amenable number.

20561137 is a deficient number, since it is larger than the sum of its proper divisors (437519).

20561137 is an equidigital number, since it uses as much as digits as its factorization.

20561137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 437518.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 20561137 is about 4534.4389950687. The cubic root of 20561137 is about 273.9569834969.

Adding to 20561137 its reverse (73116502), we get a palindrome (93677639).

The spelling of 20561137 in words is "twenty million, five hundred sixty-one thousand, one hundred thirty-seven".