7457721518521 has 4 divisors (see below), whose sum is σ = 7457727531892. Its totient is φ = 7457715505152.

The previous prime is 7457721518509. The next prime is 7457721518539. The reversal of 7457721518521 is 1258151277547.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 2307254671225 + 5150466847296 = 1518965^2 + 2269464^2 .

It is a cyclic number.

It is not a de Polignac number, because 7457721518521 - 2²⁹ = 7457184647609 is a prime.

It is a super-2 number, since 2×7457721518521² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7457721618521) 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, 383580 + ... + 3881053.

It is an arithmetic number, because the mean of its divisors is an integer number (1864431882973).

Almost surely, 2^{7457721518521} is an apocalyptic number.

It is an amenable number.

7457721518521 is a deficient number, since it is larger than the sum of its proper divisors (6013371).

7457721518521 is a wasteful number, since it uses less digits than its factorization.

7457721518521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6013370.

The product of its digits is 5488000, while the sum is 55.

The spelling of 7457721518521 in words is "seven trillion, four hundred fifty-seven billion, seven hundred twenty-one million, five hundred eighteen thousand, five hundred twenty-one".