68121521 has 4 divisors (see below), whose sum is σ = 73361652. Its totient is φ = 62881392.

The previous prime is 68121497. The next prime is 68121523. The reversal of 68121521 is 12512186.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12512186 = 2 ⋅6256093.

It can be written as a sum of positive squares in 2 ways, for example, as 21390625 + 46730896 = 4625^2 + 6836^2 .

It is a cyclic number.

It is not a de Polignac number, because 68121521 - 2⁶ = 68121457 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (68121523) 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, 2620046 + ... + 2620071.

It is an arithmetic number, because the mean of its divisors is an integer number (18340413).

Almost surely, 2^68121521 is an apocalyptic number.

It is an amenable number.

68121521 is a deficient number, since it is larger than the sum of its proper divisors (5240131).

68121521 is a wasteful number, since it uses less digits than its factorization.

68121521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5240130.

The product of its digits is 960, while the sum is 26.

The square root of 68121521 is about 8253.5762551757. The cubic root of 68121521 is about 408.4085060916.

The spelling of 68121521 in words is "sixty-eight million, one hundred twenty-one thousand, five hundred twenty-one".