81515500 has 48 divisors (see below), whose sum is σ = 194227488. Its totient is φ = 29640000.

The previous prime is 81515479. The next prime is 81515579. The reversal of 81515500 is 551518.

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1911 + ... + 12910.

It is an arithmetic number, because the mean of its divisors is an integer number (4046406).

Almost surely, 2^81515500 is an apocalyptic number.

It is an amenable number.

81515500 is an abundant number, since it is smaller than the sum of its proper divisors (112711988).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81515500 is a wasteful number, since it uses less digits than its factorization.

81515500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14851 (or 14839 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 25.

The square root of 81515500 is about 9028.5934674234. The cubic root of 81515500 is about 433.5908068815.

The spelling of 81515500 in words is "eighty-one million, five hundred fifteen thousand, five hundred".