2157979 has 4 divisors (see below), whose sum is σ = 2162376. Its totient is φ = 2153584.

The previous prime is 2157923. The next prime is 2157989. The reversal of 2157979 is 9797512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 2157979 - 2⁷ = 2157851 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2157989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1354 + ... + 2479.

It is an arithmetic number, because the mean of its divisors is an integer number (540594).

2^2157979 is an apocalyptic number.

2157979 is a deficient number, since it is larger than the sum of its proper divisors (4397).

2157979 is an equidigital number, since it uses as much as digits as its factorization.

2157979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4396.

The product of its digits is 39690, while the sum is 40.

The square root of 2157979 is about 1469.0061266040. The cubic root of 2157979 is about 129.2257529650.

It can be divided in two parts, 2157 and 979, that added together give a square (3136 = 56²).

The spelling of 2157979 in words is "two million, one hundred fifty-seven thousand, nine hundred seventy-nine".