12400821 has 12 divisors (see below), whose sum is σ = 18078060. Its totient is φ = 8190720.

The previous prime is 12400793. The next prime is 12400847. The reversal of 12400821 is 12800421.

It can be written as a sum of positive squares in 2 ways, for example, as 2852721 + 9548100 = 1689^2 + 3090^2 .

It is not a de Polignac number, because 12400821 - 2⁶ = 12400757 is a prime.

It is a super-2 number, since 2×12400821² = 307560722948082, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 12400794 and 12400803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12400721) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5340 + ... + 7301.

It is an arithmetic number, because the mean of its divisors is an integer number (1506505).

Almost surely, 2^12400821 is an apocalyptic number.

It is an amenable number.

12400821 is a deficient number, since it is larger than the sum of its proper divisors (5677239).

12400821 is a wasteful number, since it uses less digits than its factorization.

12400821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12756 (or 12753 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 12400821 is about 3521.4799445688. The cubic root of 12400821 is about 231.4640136130.

The spelling of 12400821 in words is "twelve million, four hundred thousand, eight hundred twenty-one".