19961891520 has 56 divisors (see below), whose sum is σ = 63379008624. Its totient is φ = 5323170816.

The previous prime is 19961891519. The next prime is 19961891527. The reversal of 19961891520 is 2519816991.

It is a super-2 number, since 2×19961891520² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (19961891527) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10395859 + ... + 10397778.

Almost surely, 2^19961891520 is an apocalyptic number.

19961891520 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

19961891520 is an abundant number, since it is smaller than the sum of its proper divisors (43417117104).

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

19961891520 is a wasteful number, since it uses less digits than its factorization.

19961891520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20793657 (or 20793647 counting only the distinct ones).

The product of its (nonzero) digits is 349920, while the sum is 51.

The spelling of 19961891520 in words is "nineteen billion, nine hundred sixty-one million, eight hundred ninety-one thousand, five hundred twenty".