15781997 has 16 divisors (see below), whose sum is σ = 19888512. Its totient is φ = 12165120.

The previous prime is 15781991. The next prime is 15782021. The reversal of 15781997 is 79918751.

15781997 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 15781997 - 2¹² = 15777901 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15781991) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6413 + ... + 8525.

It is an arithmetic number, because the mean of its divisors is an integer number (1243032).

Almost surely, 2^15781997 is an apocalyptic number.

It is an amenable number.

15781997 is a deficient number, since it is larger than the sum of its proper divisors (4106515).

15781997 is a wasteful number, since it uses less digits than its factorization.

15781997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2228.

The product of its digits is 158760, while the sum is 47.

The square root of 15781997 is about 3972.6561643314. The cubic root of 15781997 is about 250.8345284825.

The spelling of 15781997 in words is "fifteen million, seven hundred eighty-one thousand, nine hundred ninety-seven".