816511987540 has 12 divisors (see below), whose sum is σ = 1714675173876. Its totient is φ = 326604795008.

The previous prime is 816511987537. The next prime is 816511987583. The reversal of 816511987540 is 45789115618.

It can be written as a sum of positive squares in 2 ways, for example, as 350686627344 + 465825360196 = 592188^2 + 682514^2 .

It is a super-2 number, since 2×816511987540² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20412799669 + ... + 20412799708.

It is an arithmetic number, because the mean of its divisors is an integer number (142889597823).

Almost surely, 2^816511987540 is an apocalyptic number.

It is an amenable number.

816511987540 is an abundant number, since it is smaller than the sum of its proper divisors (898163186336).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

816511987540 is a wasteful number, since it uses less digits than its factorization.

816511987540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40825599386 (or 40825599384 counting only the distinct ones).

The product of its (nonzero) digits is 2419200, while the sum is 55.

The spelling of 816511987540 in words is "eight hundred sixteen billion, five hundred eleven million, nine hundred eighty-seven thousand, five hundred forty".