21888557 has 2 divisors, whose sum is σ = 21888558. Its totient is φ = 21888556.

The previous prime is 21888553. The next prime is 21888563. The reversal of 21888557 is 75588812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20620681 + 1267876 = 4541^2 + 1126^2 .

It is a cyclic number.

It is not a de Polignac number, because 21888557 - 2² = 21888553 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21888553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10944278 + 10944279.

It is an arithmetic number, because the mean of its divisors is an integer number (10944279).

Almost surely, 2^21888557 is an apocalyptic number.

It is an amenable number.

21888557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21888557 is an equidigital number, since it uses as much as digits as its factorization.

21888557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 179200, while the sum is 44.

The square root of 21888557 is about 4678.5208132486. The cubic root of 21888557 is about 279.7299990785.

The spelling of 21888557 in words is "twenty-one million, eight hundred eighty-eight thousand, five hundred fifty-seven".