81521299 has 2 divisors, whose sum is σ = 81521300. Its totient is φ = 81521298.

The previous prime is 81521281. The next prime is 81521309. The reversal of 81521299 is 99212518.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81521299 - 2⁹ = 81520787 is a prime.

It is not a weakly prime, because it can be changed into another prime (81591299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40760649 + 40760650.

It is an arithmetic number, because the mean of its divisors is an integer number (40760650).

Almost surely, 2^81521299 is an apocalyptic number.

81521299 is a deficient number, since it is larger than the sum of its proper divisors (1).

81521299 is an equidigital number, since it uses as much as digits as its factorization.

81521299 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 37.

The square root of 81521299 is about 9028.9146080800. The cubic root of 81521299 is about 433.6010884986.

The spelling of 81521299 in words is "eighty-one million, five hundred twenty-one thousand, two hundred ninety-nine".