20890645 has 4 divisors (see below), whose sum is σ = 25068780. Its totient is φ = 16712512.

The previous prime is 20890619. The next prime is 20890663. The reversal of 20890645 is 54609802.

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 8059921 + 12830724 = 2839^2 + 3582^2 .

It is a cyclic number.

It is not a de Polignac number, because 20890645 - 2¹⁷ = 20759573 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20890645.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2089060 + ... + 2089069.

It is an arithmetic number, because the mean of its divisors is an integer number (6267195).

Almost surely, 2^20890645 is an apocalyptic number.

It is an amenable number.

20890645 is a deficient number, since it is larger than the sum of its proper divisors (4178135).

20890645 is an equidigital number, since it uses as much as digits as its factorization.

20890645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4178134.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 20890645 is about 4570.6285125790. The cubic root of 20890645 is about 275.4126916598.

The spelling of 20890645 in words is "twenty million, eight hundred ninety thousand, six hundred forty-five".