15991223720 has 16 divisors (see below), whose sum is σ = 35980253460. Its totient is φ = 6396489472.

The previous prime is 15991223711. The next prime is 15991223747. The reversal of 15991223720 is 2732219951.

It can be written as a sum of positive squares in 2 ways, for example, as 15345758884 + 645464836 = 123878^2 + 25406^2 .

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, 199890257 + ... + 199890336.

Almost surely, 2^15991223720 is an apocalyptic number.

15991223720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

15991223720 is an abundant number, since it is smaller than the sum of its proper divisors (19989029740).

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

15991223720 is a wasteful number, since it uses less digits than its factorization.

15991223720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399780604 (or 399780600 counting only the distinct ones).

The product of its (nonzero) digits is 68040, while the sum is 41.

The spelling of 15991223720 in words is "fifteen billion, nine hundred ninety-one million, two hundred twenty-three thousand, seven hundred twenty".