20644517 has 4 divisors (see below), whose sum is σ = 20905920. Its totient is φ = 20383116.

The previous prime is 20644489. The next prime is 20644537. The reversal of 20644517 is 71544602.

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 20644517 - 2⁶ = 20644453 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20644517.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20644537) 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, 130583 + ... + 130740.

It is an arithmetic number, because the mean of its divisors is an integer number (5226480).

Almost surely, 2^20644517 is an apocalyptic number.

It is an amenable number.

20644517 is a deficient number, since it is larger than the sum of its proper divisors (261403).

20644517 is an equidigital number, since it uses as much as digits as its factorization.

20644517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261402.

The product of its (nonzero) digits is 6720, while the sum is 29.

The square root of 20644517 is about 4543.6237740376. The cubic root of 20644517 is about 274.3268029524.

The spelling of 20644517 in words is "twenty million, six hundred forty-four thousand, five hundred seventeen".