1213581 has 4 divisors (see below), whose sum is σ = 1618112. Its totient is φ = 809052.

The previous prime is 1213577. The next prime is 1213591. The reversal of 1213581 is 1853121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1853121 = 3 ⋅617707.

It is not a de Polignac number, because 1213581 - 2² = 1213577 is a prime.

It is a super-2 number, since 2×1213581² = 2945557687122, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1213561) 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, 202261 + ... + 202266.

It is an arithmetic number, because the mean of its divisors is an integer number (404528).

2^1213581 is an apocalyptic number.

It is an amenable number.

1213581 is a deficient number, since it is larger than the sum of its proper divisors (404531).

1213581 is an equidigital number, since it uses as much as digits as its factorization.

1213581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404530.

The product of its digits is 240, while the sum is 21.

The square root of 1213581 is about 1101.6265247351. The cubic root of 1213581 is about 106.6652419515.

The spelling of 1213581 in words is "one million, two hundred thirteen thousand, five hundred eighty-one".