12640021 has 2 divisors, whose sum is σ = 12640022. Its totient is φ = 12640020.

The previous prime is 12640009. The next prime is 12640037. The reversal of 12640021 is 12004621.

12640021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (12640037) can be obtained adding 12640021 to its sum of digits (16).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10817521 + 1822500 = 3289^2 + 1350^2 .

It is a cyclic number.

It is not a de Polignac number, because 12640021 - 2⁵ = 12639989 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 12639977 and 12640004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12640091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6320010 + 6320011.

It is an arithmetic number, because the mean of its divisors is an integer number (6320011).

Almost surely, 2^12640021 is an apocalyptic number.

It is an amenable number.

12640021 is a deficient number, since it is larger than the sum of its proper divisors (1).

12640021 is an equidigital number, since it uses as much as digits as its factorization.

12640021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 12640021 is about 3555.2807202807. The cubic root of 12640021 is about 232.9427859053.

Adding to 12640021 its reverse (12004621), we get a palindrome (24644642).

The spelling of 12640021 in words is "twelve million, six hundred forty thousand, twenty-one".