81899157 has 4 divisors (see below), whose sum is σ = 109198880. Its totient is φ = 54599436.

The previous prime is 81899143. The next prime is 81899173. The reversal of 81899157 is 75199818.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-81899157 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81899107) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13649857 + ... + 13649862.

It is an arithmetic number, because the mean of its divisors is an integer number (27299720).

Almost surely, 2^81899157 is an apocalyptic number.

It is an amenable number.

81899157 is a deficient number, since it is larger than the sum of its proper divisors (27299723).

81899157 is a wasteful number, since it uses less digits than its factorization.

81899157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27299722.

The product of its digits is 181440, while the sum is 48.

The square root of 81899157 is about 9049.8153019827. The cubic root of 81899157 is about 434.2699818027.

The spelling of 81899157 in words is "eighty-one million, eight hundred ninety-nine thousand, one hundred fifty-seven".