7816921 has 12 divisors (see below), whose sum is σ = 9408420. Its totient is φ = 6468000.

The previous prime is 7816891. The next prime is 7816931. The reversal of 7816921 is 1296187.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 6350400 + 1466521 = 2520^2 + 1211^2 .

It is not a de Polignac number, because 7816921 - 2⁹ = 7816409 is a prime.

It is a super-2 number, since 2×7816921² = 122208507840482, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7816931) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1330 + ... + 4171.

It is an arithmetic number, because the mean of its divisors is an integer number (784035).

Almost surely, 2^7816921 is an apocalyptic number.

It is an amenable number.

7816921 is a deficient number, since it is larger than the sum of its proper divisors (1591499).

7816921 is a wasteful number, since it uses less digits than its factorization.

7816921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5544 (or 5537 counting only the distinct ones).

The product of its digits is 6048, while the sum is 34.

The square root of 7816921 is about 2795.8757125452. The cubic root of 7816921 is about 198.4625532383.

The spelling of 7816921 in words is "seven million, eight hundred sixteen thousand, nine hundred twenty-one".