840491551 has 2 divisors, whose sum is σ = 840491552. Its totient is φ = 840491550.

The previous prime is 840491549. The next prime is 840491563. The reversal of 840491551 is 155194048.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 840491551 - 2¹ = 840491549 is a prime.

Together with 840491549, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 840491551.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (840491501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 420245775 + 420245776.

It is an arithmetic number, because the mean of its divisors is an integer number (420245776).

Almost surely, 2^840491551 is an apocalyptic number.

840491551 is a deficient number, since it is larger than the sum of its proper divisors (1).

840491551 is an equidigital number, since it uses as much as digits as its factorization.

840491551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28800, while the sum is 37.

The square root of 840491551 is about 28991.2323125458. The cubic root of 840491551 is about 943.7228067775.

The spelling of 840491551 in words is "eight hundred forty million, four hundred ninety-one thousand, five hundred fifty-one".