136518721 has 4 divisors (see below), whose sum is σ = 144549252. Its totient is φ = 128488192.

The previous prime is 136518713. The next prime is 136518749. The reversal of 136518721 is 127815631.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 127815631 = 8009 ⋅15959.

It can be written as a sum of positive squares in 2 ways, for example, as 126877696 + 9641025 = 11264^2 + 3105^2 .

It is a cyclic number.

It is not a de Polignac number, because 136518721 - 2³ = 136518713 is a prime.

It is a super-2 number, since 2×136518721² = 37274722366951682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (136518751) 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, 4015240 + ... + 4015273.

It is an arithmetic number, because the mean of its divisors is an integer number (36137313).

Almost surely, 2^136518721 is an apocalyptic number.

It is an amenable number.

136518721 is a deficient number, since it is larger than the sum of its proper divisors (8030531).

136518721 is an equidigital number, since it uses as much as digits as its factorization.

136518721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8030530.

The product of its digits is 10080, while the sum is 34.

The square root of 136518721 is about 11684.1226029172. The cubic root of 136518721 is about 514.9093012740.

The spelling of 136518721 in words is "one hundred thirty-six million, five hundred eighteen thousand, seven hundred twenty-one".