840809890997 has 4 divisors (see below), whose sum is σ = 861317449356. Its totient is φ = 820302332640.

The previous prime is 840809890937. The next prime is 840809891017. The reversal of 840809890997 is 799098908048.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 169908015601 + 670901875396 = 412199^2 + 819086^2 .

It is a cyclic number.

It is not a de Polignac number, because 840809890997 - 2¹⁰ = 840809889973 is a prime.

It is a super-2 number, since 2×840809890997² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 840809890997.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (840809890937) 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, 10253779118 + ... + 10253779199.

It is an arithmetic number, because the mean of its divisors is an integer number (215329362339).

Almost surely, 2^840809890997 is an apocalyptic number.

It is an amenable number.

840809890997 is a deficient number, since it is larger than the sum of its proper divisors (20507558359).

840809890997 is a wasteful number, since it uses less digits than its factorization.

840809890997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20507558358.

The product of its (nonzero) digits is 94058496, while the sum is 71.

The spelling of 840809890997 in words is "eight hundred forty billion, eight hundred nine million, eight hundred ninety thousand, nine hundred ninety-seven".