7816531662521 has 4 divisors (see below), whose sum is σ = 7821637171344. Its totient is φ = 7811426153700.

The previous prime is 7816531662509. The next prime is 7816531662607. The reversal of 7816531662521 is 1252661356187.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 7816531662521 - 2³⁸ = 7541653755577 is a prime.

It is a super-2 number, since 2×7816531662521² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (7816531632521) 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, 2552752115 + ... + 2552755176.

It is an arithmetic number, because the mean of its divisors is an integer number (1955409292836).

Almost surely, 2^{7816531662521} is an apocalyptic number.

It is an amenable number.

7816531662521 is a deficient number, since it is larger than the sum of its proper divisors (5105508823).

7816531662521 is a wasteful number, since it uses less digits than its factorization.

7816531662521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5105508822.

The product of its digits is 3628800, while the sum is 53.

The spelling of 7816531662521 in words is "seven trillion, eight hundred sixteen billion, five hundred thirty-one million, six hundred sixty-two thousand, five hundred twenty-one".