15640321 has 2 divisors, whose sum is σ = 15640322. Its totient is φ = 15640320.

The previous prime is 15640319. The next prime is 15640327. The reversal of 15640321 is 12304651.

15640321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15492096 + 148225 = 3936^2 + 385^2 .

It is a cyclic number.

It is not a de Polignac number, because 15640321 - 2¹ = 15640319 is a prime.

Together with 15640319, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 15640292 and 15640301.

It is not a weakly prime, because it can be changed into another prime (15640327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7820160 + 7820161.

It is an arithmetic number, because the mean of its divisors is an integer number (7820161).

Almost surely, 2^15640321 is an apocalyptic number.

It is an amenable number.

15640321 is a deficient number, since it is larger than the sum of its proper divisors (1).

15640321 is an equidigital number, since it uses as much as digits as its factorization.

15640321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 15640321 is about 3954.7845706182. The cubic root of 15640321 is about 250.0816853071.

Adding to 15640321 its reverse (12304651), we get a palindrome (27944972).

The spelling of 15640321 in words is "fifteen million, six hundred forty thousand, three hundred twenty-one".