21885257 has 2 divisors, whose sum is σ = 21885258. Its totient is φ = 21885256.

The previous prime is 21885229. The next prime is 21885263. The reversal of 21885257 is 75258812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15912121 + 5973136 = 3989^2 + 2444^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21885257 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21885257.

It is not a weakly prime, because it can be changed into another prime (21885217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10942628 + 10942629.

It is an arithmetic number, because the mean of its divisors is an integer number (10942629).

Almost surely, 2^21885257 is an apocalyptic number.

It is an amenable number.

21885257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21885257 is an equidigital number, since it uses as much as digits as its factorization.

21885257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 44800, while the sum is 38.

The square root of 21885257 is about 4678.1681243837. The cubic root of 21885257 is about 279.7159406614.

The spelling of 21885257 in words is "twenty-one million, eight hundred eighty-five thousand, two hundred fifty-seven".