12691981 has 4 divisors (see below), whose sum is σ = 13360000. Its totient is φ = 12023964.

The previous prime is 12691957. The next prime is 12691997. The reversal of 12691981 is 18919621.

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: 18919621 = 7 ⋅2702803.

It is a cyclic number.

It is not a de Polignac number, because 12691981 - 2¹³ = 12683789 is a prime.

It is a super-2 number, since 2×12691981² = 322172763408722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 12691981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12691381) 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, 333981 + ... + 334018.

It is an arithmetic number, because the mean of its divisors is an integer number (3340000).

Almost surely, 2^12691981 is an apocalyptic number.

It is an amenable number.

12691981 is a deficient number, since it is larger than the sum of its proper divisors (668019).

12691981 is an equidigital number, since it uses as much as digits as its factorization.

12691981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 668018.

The product of its digits is 7776, while the sum is 37.

The square root of 12691981 is about 3562.5806657534. The cubic root of 12691981 is about 233.2615395902.

The spelling of 12691981 in words is "twelve million, six hundred ninety-one thousand, nine hundred eighty-one".