2178991 has 2 divisors, whose sum is σ = 2178992. Its totient is φ = 2178990.

The previous prime is 2178983. The next prime is 2179007. The reversal of 2178991 is 1998712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2178991 - 2³ = 2178983 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2178991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2178191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1089495 + 1089496.

It is an arithmetic number, because the mean of its divisors is an integer number (1089496).

2^2178991 is an apocalyptic number.

2178991 is a deficient number, since it is larger than the sum of its proper divisors (1).

2178991 is an equidigital number, since it uses as much as digits as its factorization.

2178991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 37.

The square root of 2178991 is about 1476.1405759615. The cubic root of 2178991 is about 129.6438179008.

The spelling of 2178991 in words is "two million, one hundred seventy-eight thousand, nine hundred ninety-one".