7715281921 has 16 divisors (see below), whose sum is σ = 8548246224. Its totient is φ = 6931851264.

The previous prime is 7715281913. The next prime is 7715281957. The reversal of 7715281921 is 1291825177.

It can be written as a sum of positive squares in 8 ways, for example, as 3109623696 + 4605658225 = 55764^2 + 67865^2 .

It is a cyclic number.

It is not a de Polignac number, because 7715281921 - 2³ = 7715281913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7715281901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 82380 + ... + 149053.

It is an arithmetic number, because the mean of its divisors is an integer number (534265389).

Almost surely, 2^7715281921 is an apocalyptic number.

It is an amenable number.

7715281921 is a deficient number, since it is larger than the sum of its proper divisors (832964303).

7715281921 is a wasteful number, since it uses less digits than its factorization.

7715281921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 231540.

The product of its digits is 70560, while the sum is 43.

The square root of 7715281921 is about 87836.6775384862. The cubic root of 7715281921 is about 1975.9863189491.

The spelling of 7715281921 in words is "seven billion, seven hundred fifteen million, two hundred eighty-one thousand, nine hundred twenty-one".