1581002640 has 360 divisors, whose sum is σ = 6332829048. Its totient is φ = 352235520.

The previous prime is 1581002611. The next prime is 1581002641. The reversal of 1581002640 is 462001851.

1581002640 is a `hidden beast` number, since 1 + 5 + 8 + 10 + 0 + 2 + 640 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 208744704 + 1372257936 = 14448^2 + 37044^2 .

It is a tau number, because it is divible by the number of its divisors (360).

It is not an unprimeable number, because it can be changed into a prime (1581002641) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1445934 + ... + 1447026.

Almost surely, 2^1581002640 is an apocalyptic number.

1581002640 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 1581002640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3166414524).

1581002640 is an abundant number, since it is smaller than the sum of its proper divisors (4751826408).

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

1581002640 is a wasteful number, since it uses less digits than its factorization.

1581002640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1167 (or 1151 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 1581002640 is about 39761.8239018282. The cubic root of 1581002640 is about 1164.9596012196.

The spelling of 1581002640 in words is "one billion, five hundred eighty-one million, two thousand, six hundred forty".