21165587 has 2 divisors, whose sum is σ = 21165588. Its totient is φ = 21165586.

The previous prime is 21165583. The next prime is 21165593. The reversal of 21165587 is 78556112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21165587 - 2² = 21165583 is a prime.

It is not a weakly prime, because it can be changed into another prime (21165583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10582793 + 10582794.

It is an arithmetic number, because the mean of its divisors is an integer number (10582794).

Almost surely, 2^21165587 is an apocalyptic number.

21165587 is a deficient number, since it is larger than the sum of its proper divisors (1).

21165587 is an equidigital number, since it uses as much as digits as its factorization.

21165587 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16800, while the sum is 35.

The square root of 21165587 is about 4600.6072425279. The cubic root of 21165587 is about 276.6156659915.

The spelling of 21165587 in words is "twenty-one million, one hundred sixty-five thousand, five hundred eighty-seven".