81960991 has 4 divisors (see below), whose sum is σ = 93669712. Its totient is φ = 70252272.

The previous prime is 81960973. The next prime is 81961001. The reversal of 81960991 is 19906918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81960991 - 2¹³ = 81952799 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 (81960691) 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, 5854350 + ... + 5854363.

It is an arithmetic number, because the mean of its divisors is an integer number (23417428).

Almost surely, 2^81960991 is an apocalyptic number.

81960991 is a deficient number, since it is larger than the sum of its proper divisors (11708721).

81960991 is a wasteful number, since it uses less digits than its factorization.

81960991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11708720.

The product of its (nonzero) digits is 34992, while the sum is 43.

The square root of 81960991 is about 9053.2309702117. The cubic root of 81960991 is about 434.3792458291.

The spelling of 81960991 in words is "eighty-one million, nine hundred sixty thousand, nine hundred ninety-one".