2157491 has 4 divisors (see below), whose sum is σ = 2465712. Its totient is φ = 1849272.

The previous prime is 2157481. The next prime is 2157499. The reversal of 2157491 is 1947512.

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 2157491 - 2⁶ = 2157427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2157499) 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, 154100 + ... + 154113.

It is an arithmetic number, because the mean of its divisors is an integer number (616428).

2^2157491 is an apocalyptic number.

2157491 is a deficient number, since it is larger than the sum of its proper divisors (308221).

2157491 is an equidigital number, since it uses as much as digits as its factorization.

2157491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 308220.

The product of its digits is 2520, while the sum is 29.

The square root of 2157491 is about 1468.8400185180. The cubic root of 2157491 is about 129.2160113006.

The spelling of 2157491 in words is "two million, one hundred fifty-seven thousand, four hundred ninety-one".