12987921 has 4 divisors (see below), whose sum is σ = 17317232. Its totient is φ = 8658612.

The previous prime is 12987917. The next prime is 12987967. The reversal of 12987921 is 12978921.

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.

It is not a de Polignac number, because 12987921 - 2² = 12987917 is a prime.

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 12987921.

It is not an unprimeable number, because it can be changed into a prime (12987971) 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, 2164651 + ... + 2164656.

It is an arithmetic number, because the mean of its divisors is an integer number (4329308).

Almost surely, 2^12987921 is an apocalyptic number.

It is an amenable number.

12987921 is a deficient number, since it is larger than the sum of its proper divisors (4329311).

12987921 is an equidigital number, since it uses as much as digits as its factorization.

12987921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4329310.

The product of its digits is 18144, while the sum is 39.

The square root of 12987921 is about 3603.8758302694. The cubic root of 12987921 is about 235.0606211496.

The spelling of 12987921 in words is "twelve million, nine hundred eighty-seven thousand, nine hundred twenty-one".