21521299 has 2 divisors, whose sum is σ = 21521300. Its totient is φ = 21521298.

The previous prime is 21521263. The next prime is 21521317. The reversal of 21521299 is 99212512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21521299 - 2²¹ = 19424147 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21521299.

It is not a weakly prime, because it can be changed into another prime (21521249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760649 + 10760650.

It is an arithmetic number, because the mean of its divisors is an integer number (10760650).

Almost surely, 2^21521299 is an apocalyptic number.

21521299 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521299 is an equidigital number, since it uses as much as digits as its factorization.

21521299 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3240, while the sum is 31.

The square root of 21521299 is about 4639.1054094513. The cubic root of 21521299 is about 278.1566797899.

The spelling of 21521299 in words is "twenty-one million, five hundred twenty-one thousand, two hundred ninety-nine".