136391981 has 4 divisors (see below), whose sum is σ = 148791264. Its totient is φ = 123992700.

The previous prime is 136391977. The next prime is 136391987. The reversal of 136391981 is 189193631.

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, and also an emirpimes, since its reverse is a distinct semiprime: 189193631 = 11 ⋅17199421.

It is a cyclic number.

It is not a de Polignac number, because 136391981 - 2² = 136391977 is a prime.

It is a super-2 number, since 2×136391981² = 37205544962208722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (136391987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6199625 + ... + 6199646.

It is an arithmetic number, because the mean of its divisors is an integer number (37197816).

Almost surely, 2^136391981 is an apocalyptic number.

136391981 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

136391981 is a deficient number, since it is larger than the sum of its proper divisors (12399283).

136391981 is a wasteful number, since it uses less digits than its factorization.

136391981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12399282.

The product of its digits is 34992, while the sum is 41.

The square root of 136391981 is about 11678.6977441836. The cubic root of 136391981 is about 514.7499096784.

The spelling of 136391981 in words is "one hundred thirty-six million, three hundred ninety-one thousand, nine hundred eighty-one".