1581640 has 16 divisors (see below), whose sum is σ = 3558780. Its totient is φ = 632640.

The previous prime is 1581637. The next prime is 1581649. The reversal of 1581640 is 461851.

It can be written as a sum of positive squares in 2 ways, for example, as 1313316 + 268324 = 1146^2 + 518^2 .

It is not an unprimeable number, because it can be changed into a prime (1581649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19731 + ... + 19810.

2^1581640 is an apocalyptic number.

1581640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1581640 is an abundant number, since it is smaller than the sum of its proper divisors (1977140).

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

1581640 is a wasteful number, since it uses less digits than its factorization.

1581640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39552 (or 39548 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 1581640 is about 1257.6326967760. The cubic root of 1581640 is about 116.5116126132.

The spelling of 1581640 in words is "one million, five hundred eighty-one thousand, six hundred forty".