81505137 has 32 divisors (see below), whose sum is σ = 127411200. Its totient is φ = 45384768.

The previous prime is 81505133. The next prime is 81505139. The reversal of 81505137 is 73150518.

It is not a de Polignac number, because 81505137 - 2² = 81505133 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81505133) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 194314 + ... + 194732.

It is an arithmetic number, because the mean of its divisors is an integer number (3981600).

Almost surely, 2^81505137 is an apocalyptic number.

It is an amenable number.

81505137 is a deficient number, since it is larger than the sum of its proper divisors (45906063).

81505137 is a wasteful number, since it uses less digits than its factorization.

81505137 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645.

The product of its (nonzero) digits is 4200, while the sum is 30.

The square root of 81505137 is about 9028.0195502668. The cubic root of 81505137 is about 433.5724320859.

The spelling of 81505137 in words is "eighty-one million, five hundred five thousand, one hundred thirty-seven".