135168721 has 4 divisors (see below), whose sum is σ = 136155492. Its totient is φ = 134181952.

The previous prime is 135168703. The next prime is 135168749. The reversal of 135168721 is 127861531.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 65028096 + 70140625 = 8064^2 + 8375^2 .

It is a cyclic number.

It is not a de Polignac number, because 135168721 - 2¹⁷ = 135037649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (135168701) 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, 493180 + ... + 493453.

It is an arithmetic number, because the mean of its divisors is an integer number (34038873).

Almost surely, 2^135168721 is an apocalyptic number.

It is an amenable number.

135168721 is a deficient number, since it is larger than the sum of its proper divisors (986771).

135168721 is an equidigital number, since it uses as much as digits as its factorization.

135168721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 986770.

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

The square root of 135168721 is about 11626.2083673053. The cubic root of 135168721 is about 513.2064052947.

The spelling of 135168721 in words is "one hundred thirty-five million, one hundred sixty-eight thousand, seven hundred twenty-one".