1661912640 has 280 divisors, whose sum is σ = 5981696952. Its totient is φ = 437944320.

The previous prime is 1661912617. The next prime is 1661912647. The reversal of 1661912640 is 462191661.

1661912640 is a `hidden beast` number, since 1 + 6 + 6 + 1 + 9 + 1 + 2 + 640 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 318836736 + 1343075904 = 17856^2 + 36648^2 .

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 = 1661912595 and 1661912604.

It is not an unprimeable number, because it can be changed into a prime (1661912647) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 2513910 + ... + 2514570.

Almost surely, 2^1661912640 is an apocalyptic number.

1661912640 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 1661912640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2990848476).

1661912640 is an abundant number, since it is smaller than the sum of its proper divisors (4319784312).

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

1661912640 is an equidigital number, since it uses as much as digits as its factorization.

1661912640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 787 (or 768 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 1661912640 is about 40766.5627690145. The cubic root of 1661912640 is about 1184.5027235732.

The spelling of 1661912640 in words is "one billion, six hundred sixty-one million, nine hundred twelve thousand, six hundred forty".