81513959 has 4 divisors (see below), whose sum is σ = 81700080. Its totient is φ = 81327840.

The previous prime is 81513941. The next prime is 81513961. The reversal of 81513959 is 95931518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 95931518 = 2 ⋅47965759.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81513959 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 (81513919) 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, 92402 + ... + 93279.

It is an arithmetic number, because the mean of its divisors is an integer number (20425020).

Almost surely, 2^81513959 is an apocalyptic number.

81513959 is a deficient number, since it is larger than the sum of its proper divisors (186121).

81513959 is a wasteful number, since it uses less digits than its factorization.

81513959 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 186120.

The product of its digits is 48600, while the sum is 41.

The square root of 81513959 is about 9028.5081270385. The cubic root of 81513959 is about 433.5880746092.

The spelling of 81513959 in words is "eighty-one million, five hundred thirteen thousand, nine hundred fifty-nine".