136640721 has 32 divisors (see below), whose sum is σ = 217900800. Its totient is φ = 74511360.

The previous prime is 136640689. The next prime is 136640737. The reversal of 136640721 is 127046631.

It is not a de Polignac number, because 136640721 - 2⁵ = 136640689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (136640321) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 52941 + ... + 55461.

It is an arithmetic number, because the mean of its divisors is an integer number (6809400).

Almost surely, 2^136640721 is an apocalyptic number.

It is an amenable number.

136640721 is a deficient number, since it is larger than the sum of its proper divisors (81260079).

136640721 is a wasteful number, since it uses less digits than its factorization.

136640721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2649.

The product of its (nonzero) digits is 6048, while the sum is 30.

The square root of 136640721 is about 11689.3421970614. The cubic root of 136640721 is about 515.0626385620.

The spelling of 136640721 in words is "one hundred thirty-six million, six hundred forty thousand, seven hundred twenty-one".