19961640 has 160 divisors (see below), whose sum is σ = 68868360. Its totient is φ = 5184000.

The previous prime is 19961639. The next prime is 19961653. The reversal of 19961640 is 4616991.

19961640 is a `hidden beast` number, since 1 + 9 + 9 + 6 + 1 + 640 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 15824484 + 4137156 = 3978^2 + 2034^2 .

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 = 19961595 and 19961604.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 197590 + ... + 197690.

Almost surely, 2^19961640 is an apocalyptic number.

19961640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19961640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34434180).

19961640 is an abundant number, since it is smaller than the sum of its proper divisors (48906720).

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

19961640 is a wasteful number, since it uses less digits than its factorization.

19961640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185 (or 172 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 19961640 is about 4467.8451181750. The cubic root of 19961640 is about 271.2681088238.

The spelling of 19961640 in words is "nineteen million, nine hundred sixty-one thousand, six hundred forty".