12689721 has 24 divisors (see below), whose sum is σ = 20869056. Its totient is φ = 7355040.

The previous prime is 12689711. The next prime is 12689731. The reversal of 12689721 is 12798621.

It is an interprime number because it is at equal distance from previous prime (12689711) and next prime (12689731).

It is not a de Polignac number, because 12689721 - 2⁵ = 12689689 is a prime.

It is a super-2 number, since 2×12689721² = 322058038115682, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (12689711) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 510 + ... + 5063.

It is an arithmetic number, because the mean of its divisors is an integer number (869544).

Almost surely, 2^12689721 is an apocalyptic number.

12689721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

12689721 is a deficient number, since it is larger than the sum of its proper divisors (8179335).

12689721 is a wasteful number, since it uses less digits than its factorization.

12689721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5613 (or 5610 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 12689721 is about 3562.2634658318. The cubic root of 12689721 is about 233.2476935150.

Subtracting 12689721 from its reverse (12798621), we obtain a square (108900 = 330²).

The spelling of 12689721 in words is "twelve million, six hundred eighty-nine thousand, seven hundred twenty-one".