7940021 has 2 divisors, whose sum is σ = 7940022. Its totient is φ = 7940020.

The previous prime is 7940017. The next prime is 7940047. The reversal of 7940021 is 1200497.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7236100 + 703921 = 2690^2 + 839^2 .

It is a cyclic number.

It is not a de Polignac number, because 7940021 - 2² = 7940017 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7940011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3970010 + 3970011.

It is an arithmetic number, because the mean of its divisors is an integer number (3970011).

Almost surely, 2^7940021 is an apocalyptic number.

It is an amenable number.

7940021 is a deficient number, since it is larger than the sum of its proper divisors (1).

7940021 is an equidigital number, since it uses as much as digits as its factorization.

7940021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 7940021 is about 2817.8042870292. The cubic root of 7940021 is about 199.4989206458.

The spelling of 7940021 in words is "seven million, nine hundred forty thousand, twenty-one".