81211523 has 2 divisors, whose sum is σ = 81211524. Its totient is φ = 81211522.

The previous prime is 81211469. The next prime is 81211573. The reversal of 81211523 is 32511218.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81211523 - 2²² = 77017219 is a prime.

It is a super-2 number, since 2×81211523² = 13190622935959058, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81211573) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40605761 + 40605762.

It is an arithmetic number, because the mean of its divisors is an integer number (40605762).

Almost surely, 2^81211523 is an apocalyptic number.

81211523 is a deficient number, since it is larger than the sum of its proper divisors (1).

81211523 is an equidigital number, since it uses as much as digits as its factorization.

81211523 is an evil number, because the sum of its binary digits is even.

The product of its digits is 480, while the sum is 23.

The square root of 81211523 is about 9011.7436159713. The cubic root of 81211523 is about 433.0511720658.

The spelling of 81211523 in words is "eighty-one million, two hundred eleven thousand, five hundred twenty-three".