1581165440 has 64 divisors (see below), whose sum is σ = 3791340000. Its totient is φ = 630564864.

The previous prime is 1581165413. The next prime is 1581165517. The reversal of 1581165440 is 445611851.

It is a tau number, because it is divible by the number of its divisors (64).

It is a self number, because there is not a number n which added to its sum of digits gives 1581165440.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 219821 + ... + 226899.

Almost surely, 2^1581165440 is an apocalyptic number.

1581165440 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 1581165440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1895670000).

1581165440 is an abundant number, since it is smaller than the sum of its proper divisors (2210174560).

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

1581165440 is an equidigital number, since it uses as much as digits as its factorization.

1581165440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7447 (or 7435 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 35.

The square root of 1581165440 is about 39763.8710389218. The cubic root of 1581165440 is about 1164.9995861653. Note that the first 3 decimals are identical.

The spelling of 1581165440 in words is "one billion, five hundred eighty-one million, one hundred sixty-five thousand, four hundred forty".