21856889 has 2 divisors, whose sum is σ = 21856890. Its totient is φ = 21856888.

The previous prime is 21856873. The next prime is 21856903. The reversal of 21856889 is 98865812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13446889 + 8410000 = 3667^2 + 2900^2 .

It is a cyclic number.

It is not a de Polignac number, because 21856889 - 2⁴ = 21856873 is a prime.

It is not a weakly prime, because it can be changed into another prime (21856189) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10928444 + 10928445.

It is an arithmetic number, because the mean of its divisors is an integer number (10928445).

Almost surely, 2^21856889 is an apocalyptic number.

It is an amenable number.

21856889 is a deficient number, since it is larger than the sum of its proper divisors (1).

21856889 is an equidigital number, since it uses as much as digits as its factorization.

21856889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 276480, while the sum is 47.

The square root of 21856889 is about 4675.1351852112. The cubic root of 21856889 is about 279.5950310653.

The spelling of 21856889 in words is "twenty-one million, eight hundred fifty-six thousand, eight hundred eighty-nine".