20865221 has 4 divisors (see below), whose sum is σ = 22470252. Its totient is φ = 19260192.

The previous prime is 20865217. The next prime is 20865253. The reversal of 20865221 is 12256802.

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 3940225 + 16924996 = 1985^2 + 4114^2 .

It is a cyclic number.

It is not a de Polignac number, because 20865221 - 2² = 20865217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20865281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 802496 + ... + 802521.

It is an arithmetic number, because the mean of its divisors is an integer number (5617563).

Almost surely, 2^20865221 is an apocalyptic number.

It is an amenable number.

20865221 is a deficient number, since it is larger than the sum of its proper divisors (1605031).

20865221 is a wasteful number, since it uses less digits than its factorization.

20865221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1605030.

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 20865221 is about 4567.8464291173. The cubic root of 20865221 is about 275.3009201832.

The spelling of 20865221 in words is "twenty million, eight hundred sixty-five thousand, two hundred twenty-one".