20879561 has 4 divisors (see below), whose sum is σ = 21787392. Its totient is φ = 19971732.

The previous prime is 20879531. The next prime is 20879567. The reversal of 20879561 is 16597802.

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 20879561 - 2⁶ = 20879497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20879567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 453881 + ... + 453926.

It is an arithmetic number, because the mean of its divisors is an integer number (5446848).

Almost surely, 2^20879561 is an apocalyptic number.

It is an amenable number.

20879561 is a deficient number, since it is larger than the sum of its proper divisors (907831).

20879561 is an equidigital number, since it uses as much as digits as its factorization.

20879561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 907830.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 20879561 is about 4569.4158269958. The cubic root of 20879561 is about 275.3639742503.

The spelling of 20879561 in words is "twenty million, eight hundred seventy-nine thousand, five hundred sixty-one".