1581581 has 2 divisors, whose sum is σ = 1581582. Its totient is φ = 1581580.

The previous prime is 1581577. The next prime is 1581607. The reversal of 1581581 is 1851851.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1322500 + 259081 = 1150^2 + 509^2 .

It is an emirp because it is prime and its reverse (1851851) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1581581 - 2² = 1581577 is a prime.

It is a super-2 number, since 2×1581581² = 5002796919122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1580581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 790790 + 790791.

It is an arithmetic number, because the mean of its divisors is an integer number (790791).

2^1581581 is an apocalyptic number.

It is an amenable number.

1581581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1581581 is an equidigital number, since it uses as much as digits as its factorization.

1581581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1600, while the sum is 29.

The square root of 1581581 is about 1257.6092397879. The cubic root of 1581581 is about 116.5101638489.

The spelling of 1581581 in words is "one million, five hundred eighty-one thousand, five hundred eighty-one".