7890921 has 6 divisors (see below), whose sum is σ = 11398010. Its totient is φ = 5260608.

The previous prime is 7890919. The next prime is 7890923. The reversal of 7890921 is 1290987.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (7890919) and next prime (7890923).

It can be written as a sum of positive squares in only one way, i.e., 7080921 + 810000 = 2661^2 + 900^2 .

It is not a de Polignac number, because 7890921 - 2¹ = 7890919 is a prime.

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 (7890923) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 438376 + ... + 438393.

Almost surely, 2^7890921 is an apocalyptic number.

It is an amenable number.

7890921 is a deficient number, since it is larger than the sum of its proper divisors (3507089).

7890921 is a wasteful number, since it uses less digits than its factorization.

7890921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 876775 (or 876772 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 7890921 is about 2809.0783185949. The cubic root of 7890921 is about 199.0868454222.

The spelling of 7890921 in words is "seven million, eight hundred ninety thousand, nine hundred twenty-one".