840878257 has 2 divisors, whose sum is σ = 840878258. Its totient is φ = 840878256.

The previous prime is 840878249. The next prime is 840878261. The reversal of 840878257 is 752878048.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 641051761 + 199826496 = 25319^2 + 14136^2 .

It is a cyclic number.

It is not a de Polignac number, because 840878257 - 2³ = 840878249 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 840878257.

It is not a weakly prime, because it can be changed into another prime (840878237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 420439128 + 420439129.

It is an arithmetic number, because the mean of its divisors is an integer number (420439129).

Almost surely, 2^840878257 is an apocalyptic number.

It is an amenable number.

840878257 is a deficient number, since it is larger than the sum of its proper divisors (1).

840878257 is an equidigital number, since it uses as much as digits as its factorization.

840878257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1003520, while the sum is 49.

The square root of 840878257 is about 28997.9009067898. The cubic root of 840878257 is about 943.8675186492.

The spelling of 840878257 in words is "eight hundred forty million, eight hundred seventy-eight thousand, two hundred fifty-seven".