81215955 has 12 divisors (see below), whose sum is σ = 140774400. Its totient is φ = 43315152.

The previous prime is 81215951. The next prime is 81215963. The reversal of 81215955 is 55951218.

It is a happy number.

It is not a de Polignac number, because 81215955 - 2² = 81215951 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81215951) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 902355 + ... + 902444.

It is an arithmetic number, because the mean of its divisors is an integer number (11731200).

Almost surely, 2^81215955 is an apocalyptic number.

81215955 is a deficient number, since it is larger than the sum of its proper divisors (59558445).

81215955 is a wasteful number, since it uses less digits than its factorization.

81215955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1804810 (or 1804807 counting only the distinct ones).

The product of its digits is 18000, while the sum is 36.

The square root of 81215955 is about 9011.9895139753. The cubic root of 81215955 is about 433.0590496338.

The spelling of 81215955 in words is "eighty-one million, two hundred fifteen thousand, nine hundred fifty-five".