21065599 has 2 divisors, whose sum is σ = 21065600. Its totient is φ = 21065598.

The previous prime is 21065563. The next prime is 21065609. The reversal of 21065599 is 99556012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21065599 - 2²³ = 12676991 is a prime.

It is a super-2 number, since 2×21065599² = 887518922457602, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21065549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10532799 + 10532800.

It is an arithmetic number, because the mean of its divisors is an integer number (10532800).

Almost surely, 2^21065599 is an apocalyptic number.

21065599 is a deficient number, since it is larger than the sum of its proper divisors (1).

21065599 is an equidigital number, since it uses as much as digits as its factorization.

21065599 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24300, while the sum is 37.

The square root of 21065599 is about 4589.7275518270. The cubic root of 21065599 is about 276.1793931055.

It can be divided in two parts, 2 and 1065599, that added together give a palindrome (1065601).

The spelling of 21065599 in words is "twenty-one million, sixty-five thousand, five hundred ninety-nine".