136721261 has 4 divisors (see below), whose sum is σ = 139630272. Its totient is φ = 133812252.

The previous prime is 136721251. The next prime is 136721267. The reversal of 136721261 is 162127631.

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: 162127631 = 359 ⋅451609.

It is a cyclic number.

It is not a de Polignac number, because 136721261 - 2⁶ = 136721197 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 (136721267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1454435 + ... + 1454528.

It is an arithmetic number, because the mean of its divisors is an integer number (34907568).

Almost surely, 2^136721261 is an apocalyptic number.

It is an amenable number.

136721261 is a deficient number, since it is larger than the sum of its proper divisors (2909011).

136721261 is an equidigital number, since it uses as much as digits as its factorization.

136721261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2909010.

The product of its digits is 3024, while the sum is 29.

The square root of 136721261 is about 11692.7867080521. The cubic root of 136721261 is about 515.1638162998.

Adding to 136721261 its reverse (162127631), we get a palindrome (298848892).

The spelling of 136721261 in words is "one hundred thirty-six million, seven hundred twenty-one thousand, two hundred sixty-one".