15813781956 has 216 divisors, whose sum is σ = 51061491936. Its totient is φ = 4252227840.

The previous prime is 15813781931. The next prime is 15813781961. The reversal of 15813781956 is 65918731851.

It is a happy number.

15813781956 is a `hidden beast` number, since 1 + 5 + 81 + 378 + 195 + 6 = 666.

15813781956 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-3 number, since 3×15813781956³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 799911 + ... + 819441.

It is an arithmetic number, because the mean of its divisors is an integer number (236395796).

Almost surely, 2^15813781956 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 15813781956, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25530745968).

15813781956 is an abundant number, since it is smaller than the sum of its proper divisors (35247709980).

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

15813781956 is a wasteful number, since it uses less digits than its factorization.

15813781956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19581 (or 19560 counting only the distinct ones).

The product of its digits is 1814400, while the sum is 54.

The spelling of 15813781956 in words is "fifteen billion, eight hundred thirteen million, seven hundred eighty-one thousand, nine hundred fifty-six".