81520505 has 16 divisors (see below), whose sum is σ = 109323648. Its totient is φ = 57840000.

The previous prime is 81520501. The next prime is 81520553. The reversal of 81520505 is 50502518.

It is not a de Polignac number, because 81520505 - 2² = 81520501 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81520501) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15821 + ... + 20330.

It is an arithmetic number, because the mean of its divisors is an integer number (6832728).

Almost surely, 2^81520505 is an apocalyptic number.

It is an amenable number.

81520505 is a deficient number, since it is larger than the sum of its proper divisors (27803143).

81520505 is a wasteful number, since it uses less digits than its factorization.

81520505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36208.

The product of its (nonzero) digits is 2000, while the sum is 26.

The square root of 81520505 is about 9028.8706381252. The cubic root of 81520505 is about 433.5996807668.

The spelling of 81520505 in words is "eighty-one million, five hundred twenty thousand, five hundred five".