7515721 has 2 divisors, whose sum is σ = 7515722. Its totient is φ = 7515720.

The previous prime is 7515719. The next prime is 7515731. The reversal of 7515721 is 1275157.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6969600 + 546121 = 2640^2 + 739^2 .

It is a cyclic number.

It is not a de Polignac number, because 7515721 - 2¹ = 7515719 is a prime.

Together with 7515719, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 7515721.

It is not a weakly prime, because it can be changed into another prime (7515731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3757860 + 3757861.

It is an arithmetic number, because the mean of its divisors is an integer number (3757861).

Almost surely, 2^7515721 is an apocalyptic number.

It is an amenable number.

7515721 is a deficient number, since it is larger than the sum of its proper divisors (1).

7515721 is an equidigital number, since it uses as much as digits as its factorization.

7515721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2450, while the sum is 28.

The square root of 7515721 is about 2741.4815337697. The cubic root of 7515721 is about 195.8800546842.

The spelling of 7515721 in words is "seven million, five hundred fifteen thousand, seven hundred twenty-one".