7977921 has 32 divisors (see below), whose sum is σ = 12718080. Its totient is φ = 4354176.

The previous prime is 7977899. The next prime is 7977923. The reversal of 7977921 is 1297797.

It is not a de Polignac number, because 7977921 - 2⁶ = 7977857 is a prime.

It is a super-5 number, since 5×7977921⁵ (a number of 36 digits) contains 55555 as substring.

It is not an unprimeable number, because it can be changed into a prime (7977923) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 58165 + ... + 58301.

It is an arithmetic number, because the mean of its divisors is an integer number (397440).

Almost surely, 2^7977921 is an apocalyptic number.

It is an amenable number.

7977921 is a deficient number, since it is larger than the sum of its proper divisors (4740159).

7977921 is a wasteful number, since it uses less digits than its factorization.

7977921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253.

The product of its digits is 55566, while the sum is 42.

The square root of 7977921 is about 2824.5213753838. The cubic root of 7977921 is about 199.8158388087.

It can be divided in two parts, 79779 and 21, that added together give a triangular number (79800 = T₃₉₉).

The spelling of 7977921 in words is "seven million, nine hundred seventy-seven thousand, nine hundred twenty-one".