81915387 has 8 divisors (see below), whose sum is σ = 111760704. Its totient is φ = 53340168.

The previous prime is 81915371. The next prime is 81915389. The reversal of 81915387 is 78351918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81915387 - 2⁴ = 81915371 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81915389) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 317373 + ... + 317630.

It is an arithmetic number, because the mean of its divisors is an integer number (13970088).

Almost surely, 2^81915387 is an apocalyptic number.

81915387 is a deficient number, since it is larger than the sum of its proper divisors (29845317).

81915387 is a wasteful number, since it uses less digits than its factorization.

81915387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 635049.

The product of its digits is 60480, while the sum is 42.

The square root of 81915387 is about 9050.7119609454. The cubic root of 81915387 is about 434.2986664133.

The spelling of 81915387 in words is "eighty-one million, nine hundred fifteen thousand, three hundred eighty-seven".