7816721 has 6 divisors (see below), whose sum is σ = 8592066. Its totient is φ = 7106000.

The previous prime is 7816709. The next prime is 7816727. The reversal of 7816721 is 1276187.

It can be written as a sum of positive squares in only one way, i.e., 7623121 + 193600 = 2761^2 + 440^2 .

It is not a de Polignac number, because 7816721 - 2¹⁴ = 7800337 is a prime.

It is a super-2 number, since 2×7816721² = 122202254383682, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7816727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 32180 + ... + 32421.

It is an arithmetic number, because the mean of its divisors is an integer number (1432011).

Almost surely, 2^7816721 is an apocalyptic number.

It is an amenable number.

7816721 is a deficient number, since it is larger than the sum of its proper divisors (775345).

7816721 is a wasteful number, since it uses less digits than its factorization.

7816721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64623 (or 64612 counting only the distinct ones).

The product of its digits is 4704, while the sum is 32.

The square root of 7816721 is about 2795.8399453474. The cubic root of 7816721 is about 198.4608606346.

The spelling of 7816721 in words is "seven million, eight hundred sixteen thousand, seven hundred twenty-one".