20628561 has 4 divisors (see below), whose sum is σ = 27504752. Its totient is φ = 13752372.

The previous prime is 20628557. The next prime is 20628581. The reversal of 20628561 is 16582602.

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 not a de Polignac number, because 20628561 - 2² = 20628557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20628521) 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 in 3 ways as a sum of consecutive naturals, for example, 3438091 + ... + 3438096.

It is an arithmetic number, because the mean of its divisors is an integer number (6876188).

Almost surely, 2^20628561 is an apocalyptic number.

It is an amenable number.

20628561 is a deficient number, since it is larger than the sum of its proper divisors (6876191).

20628561 is an equidigital number, since it uses as much as digits as its factorization.

20628561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6876190.

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 20628561 is about 4541.8675674220. The cubic root of 20628561 is about 274.2561096598.

The spelling of 20628561 in words is "twenty million, six hundred twenty-eight thousand, five hundred sixty-one".