21087569 has 2 divisors, whose sum is σ = 21087570. Its totient is φ = 21087568.

The previous prime is 21087557. The next prime is 21087581. The reversal of 21087569 is 96578012.

It is a balanced prime because it is at equal distance from previous prime (21087557) and next prime (21087581).

It can be written as a sum of positive squares in only one way, i.e., 16507969 + 4579600 = 4063^2 + 2140^2 .

It is a cyclic number.

It is not a de Polignac number, because 21087569 - 2²⁴ = 4310353 is a prime.

It is a super-2 number, since 2×21087569² = 889371132659522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21087529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10543784 + 10543785.

It is an arithmetic number, because the mean of its divisors is an integer number (10543785).

Almost surely, 2^21087569 is an apocalyptic number.

It is an amenable number.

21087569 is a deficient number, since it is larger than the sum of its proper divisors (1).

21087569 is an equidigital number, since it uses as much as digits as its factorization.

21087569 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 21087569 is about 4592.1203163680. The cubic root of 21087569 is about 276.2753719113.

The spelling of 21087569 in words is "twenty-one million, eighty-seven thousand, five hundred sixty-nine".