20215665 has 24 divisors (see below), whose sum is σ = 35898408. Its totient is φ = 10517760.

The previous prime is 20215661. The next prime is 20215667. The reversal of 20215665 is 56651202.

It can be written as a sum of positive squares in 4 ways, for example, as 207936 + 20007729 = 456^2 + 4473^2 .

It is not a de Polignac number, because 20215665 - 2² = 20215661 is a prime.

It is a super-2 number, since 2×20215665² = 817346222784450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20215661) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3634 + ... + 7323.

It is an arithmetic number, because the mean of its divisors is an integer number (1495767).

Almost surely, 2^20215665 is an apocalyptic number.

It is an amenable number.

20215665 is a deficient number, since it is larger than the sum of its proper divisors (15682743).

20215665 is a wasteful number, since it uses less digits than its factorization.

20215665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11009 (or 11006 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 20215665 is about 4496.1833814915. The cubic root of 20215665 is about 272.4139503293.

Adding to 20215665 its reverse (56651202), we get a palindrome (76866867).

The spelling of 20215665 in words is "twenty million, two hundred fifteen thousand, six hundred sixty-five".