840491561 has 36 divisors (see below), whose sum is σ = 1088776836. Its totient is φ = 643083840.

The previous prime is 840491551. The next prime is 840491563. The reversal of 840491561 is 165194048.

It can be written as a sum of positive squares in 2 ways, for example, as 539121961 + 301369600 = 23219^2 + 17360^2 .

It is a de Polignac number, because none of the positive numbers 2^k-840491561 is a prime.

It is a super-3 number, since 3×840491561³ (a number of 28 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (840491563) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 611471 + ... + 612843.

It is an arithmetic number, because the mean of its divisors is an integer number (30243801).

Almost surely, 2^840491561 is an apocalyptic number.

It is an amenable number.

840491561 is a deficient number, since it is larger than the sum of its proper divisors (248285275).

840491561 is a wasteful number, since it uses less digits than its factorization.

840491561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1462 (or 1424 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 38.

The square root of 840491561 is about 28991.2324850117. The cubic root of 840491561 is about 943.7228105203.

The spelling of 840491561 in words is "eight hundred forty million, four hundred ninety-one thousand, five hundred sixty-one".