20873561 has 4 divisors (see below), whose sum is σ = 20920500. Its totient is φ = 20826624.

The previous prime is 20873539. The next prime is 20873563. The reversal of 20873561 is 16537802.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10601536 + 10272025 = 3256^2 + 3205^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20873561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20873563) 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, 22796 + ... + 23693.

It is an arithmetic number, because the mean of its divisors is an integer number (5230125).

Almost surely, 2^20873561 is an apocalyptic number.

It is an amenable number.

20873561 is a deficient number, since it is larger than the sum of its proper divisors (46939).

20873561 is an equidigital number, since it uses as much as digits as its factorization.

20873561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46938.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 20873561 is about 4568.7592407567. The cubic root of 20873561 is about 275.3375953092.

The spelling of 20873561 in words is "twenty million, eight hundred seventy-three thousand, five hundred sixty-one".