81520199 has 2 divisors, whose sum is σ = 81520200. Its totient is φ = 81520198.

The previous prime is 81520171. The next prime is 81520223. The reversal of 81520199 is 99102518.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81520199 - 2¹⁶ = 81454663 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81520129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40760099 + 40760100.

It is an arithmetic number, because the mean of its divisors is an integer number (40760100).

Almost surely, 2^81520199 is an apocalyptic number.

81520199 is a deficient number, since it is larger than the sum of its proper divisors (1).

81520199 is an equidigital number, since it uses as much as digits as its factorization.

81520199 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 35.

The square root of 81520199 is about 9028.8536924684. The cubic root of 81520199 is about 433.5991382379.

The spelling of 81520199 in words is "eighty-one million, five hundred twenty thousand, one hundred ninety-nine".