81961511 has 8 divisors (see below), whose sum is σ = 85108800. Its totient is φ = 78835680.

The previous prime is 81961493. The next prime is 81961513. The reversal of 81961511 is 11516918.

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

It is a cyclic number.

It is not a de Polignac number, because 81961511 - 2²⁶ = 14852647 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 (81961513) 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, 2645 + ... + 13073.

It is an arithmetic number, because the mean of its divisors is an integer number (10638600).

Almost surely, 2^81961511 is an apocalyptic number.

81961511 is a deficient number, since it is larger than the sum of its proper divisors (3147289).

81961511 is a wasteful number, since it uses less digits than its factorization.

81961511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10729.

The product of its digits is 2160, while the sum is 32.

The square root of 81961511 is about 9053.2596891948. The cubic root of 81961511 is about 434.3801644642.

The spelling of 81961511 in words is "eighty-one million, nine hundred sixty-one thousand, five hundred eleven".