15438991 has 4 divisors (see below), whose sum is σ = 15971400. Its totient is φ = 14906584.

The previous prime is 15438947. The next prime is 15439019. The reversal of 15438991 is 19983451.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19983451 = 1013 ⋅19727.

It is a cyclic number.

It is not a de Polignac number, because 15438991 - 2¹¹ = 15436943 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15438931) 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, 266161 + ... + 266218.

It is an arithmetic number, because the mean of its divisors is an integer number (3992850).

Almost surely, 2^15438991 is an apocalyptic number.

15438991 is a deficient number, since it is larger than the sum of its proper divisors (532409).

15438991 is an equidigital number, since it uses as much as digits as its factorization.

15438991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 532408.

The product of its digits is 38880, while the sum is 40.

The square root of 15438991 is about 3929.2481469106. The cubic root of 15438991 is about 249.0039891191.

The spelling of 15438991 in words is "fifteen million, four hundred thirty-eight thousand, nine hundred ninety-one".