81961131 has 16 divisors (see below), whose sum is σ = 132240384. Its totient is φ = 44079744.

The previous prime is 81961129. The next prime is 81961169. The reversal of 81961131 is 13116918.

It is not a de Polignac number, because 81961131 - 2¹ = 81961129 is a prime.

It is a super-2 number, since 2×81961131² = 13435253989598322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81961111) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 114435 + ... + 115148.

It is an arithmetic number, because the mean of its divisors is an integer number (8265024).

Almost surely, 2^81961131 is an apocalyptic number.

81961131 is a deficient number, since it is larger than the sum of its proper divisors (50279253).

81961131 is a wasteful number, since it uses less digits than its factorization.

81961131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 229610.

The product of its digits is 1296, while the sum is 30.

The square root of 81961131 is about 9053.2387022546. The cubic root of 81961131 is about 434.3794931544.

The spelling of 81961131 in words is "eighty-one million, nine hundred sixty-one thousand, one hundred thirty-one".