19891521378 has 40 divisors (see below), whose sum is σ = 45658873260. Its totient is φ = 6468785280.

The previous prime is 19891521371. The next prime is 19891521389. The reversal of 19891521378 is 87312519891.

19891521378 is a `hidden beast` number, since 1 + 9 + 89 + 1 + 521 + 37 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 15914579409 + 3976941969 = 126153^2 + 63063^2 .

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

It is not an unprimeable number, because it can be changed into a prime (19891521371) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1490763 + ... + 1504046.

Almost surely, 2^19891521378 is an apocalyptic number.

19891521378 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

19891521378 is an abundant number, since it is smaller than the sum of its proper divisors (25767351882).

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

19891521378 is a wasteful number, since it uses less digits than its factorization.

19891521378 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2994864 (or 2994855 counting only the distinct ones).

The product of its digits is 1088640, while the sum is 54.

The spelling of 19891521378 in words is "nineteen billion, eight hundred ninety-one million, five hundred twenty-one thousand, three hundred seventy-eight".