20645617 has 4 divisors (see below), whose sum is σ = 20656116. Its totient is φ = 20635120.

The previous prime is 20645579. The next prime is 20645671. The reversal of 20645617 is 71654602.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 9991921 + 10653696 = 3161^2 + 3264^2 .

It is a cyclic number.

It is not a de Polignac number, because 20645617 - 2²³ = 12257009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20645917) 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, 1318 + ... + 6559.

It is an arithmetic number, because the mean of its divisors is an integer number (5164029).

Almost surely, 2^20645617 is an apocalyptic number.

It is an amenable number.

20645617 is a deficient number, since it is larger than the sum of its proper divisors (10499).

20645617 is an equidigital number, since it uses as much as digits as its factorization.

20645617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10498.

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 20645617 is about 4543.7448211800. The cubic root of 20645617 is about 274.3316751762.

The spelling of 20645617 in words is "twenty million, six hundred forty-five thousand, six hundred seventeen".