21738387 has 16 divisors (see below), whose sum is σ = 32140800. Its totient is φ = 12957600.

The previous prime is 21738361. The next prime is 21738389. The reversal of 21738387 is 78383712.

It is not a de Polignac number, because 21738387 - 2⁷ = 21738259 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21738389) 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, 3387 + ... + 7412.

It is an arithmetic number, because the mean of its divisors is an integer number (2008800).

Almost surely, 2^21738387 is an apocalyptic number.

21738387 is a deficient number, since it is larger than the sum of its proper divisors (10402413).

21738387 is a wasteful number, since it uses less digits than its factorization.

21738387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10874.

The product of its digits is 56448, while the sum is 39.

The square root of 21738387 is about 4662.4443160214. Note that the first 3 decimals coincide. The cubic root of 21738387 is about 279.0888195008.

It can be divided in two parts, 217383 and 87, that added together give a triangular number (217470 = T₆₅₉).

The spelling of 21738387 in words is "twenty-one million, seven hundred thirty-eight thousand, three hundred eighty-seven".