1581397 has 4 divisors (see below), whose sum is σ = 1590316. Its totient is φ = 1572480.

The previous prime is 1581379. The next prime is 1581413. The reversal of 1581397 is 7931851.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7931851 = 251 ⋅31601.

It can be written as a sum of positive squares in 2 ways, for example, as 221841 + 1359556 = 471^2 + 1166^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1581397 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1581317) 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, 4188 + ... + 4549.

It is an arithmetic number, because the mean of its divisors is an integer number (397579).

2^1581397 is an apocalyptic number.

It is an amenable number.

1581397 is a deficient number, since it is larger than the sum of its proper divisors (8919).

1581397 is an equidigital number, since it uses as much as digits as its factorization.

1581397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8918.

The product of its digits is 7560, while the sum is 34.

The square root of 1581397 is about 1257.5360829813. The cubic root of 1581397 is about 116.5056454373.

The spelling of 1581397 in words is "one million, five hundred eighty-one thousand, three hundred ninety-seven".