19891440 has 80 divisors (see below), whose sum is σ = 68522400. Its totient is φ = 5303808.

The previous prime is 19891439. The next prime is 19891453. The reversal of 19891440 is 4419891.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 19891395 and 19891404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2445 + ... + 6764.

It is an arithmetic number, because the mean of its divisors is an integer number (856530).

Almost surely, 2^19891440 is an apocalyptic number.

19891440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

19891440 is an abundant number, since it is smaller than the sum of its proper divisors (48630960).

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

19891440 is a wasteful number, since it uses less digits than its factorization.

19891440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9231 (or 9219 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The square root of 19891440 is about 4459.9820627442. The cubic root of 19891440 is about 270.9497417273.

The spelling of 19891440 in words is "nineteen million, eight hundred ninety-one thousand, four hundred forty".