15640397 has 4 divisors (see below), whose sum is σ = 15660540. Its totient is φ = 15620256.

The previous prime is 15640379. The next prime is 15640403. The reversal of 15640397 is 79304651.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14280841 + 1359556 = 3779^2 + 1166^2 .

It is a cyclic number.

It is not a de Polignac number, because 15640397 - 2¹² = 15636301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15640327) 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, 8858 + ... + 10475.

It is an arithmetic number, because the mean of its divisors is an integer number (3915135).

Almost surely, 2^15640397 is an apocalyptic number.

It is an amenable number.

15640397 is a deficient number, since it is larger than the sum of its proper divisors (20143).

15640397 is an equidigital number, since it uses as much as digits as its factorization.

15640397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20142.

The product of its (nonzero) digits is 22680, while the sum is 35.

The square root of 15640397 is about 3954.7941792210. The cubic root of 15640397 is about 250.0820903751.

The spelling of 15640397 in words is "fifteen million, six hundred forty thousand, three hundred ninety-seven".