21378842 has 4 divisors (see below), whose sum is σ = 32068266. Its totient is φ = 10689420.

The previous prime is 21378817. The next prime is 21378883. The reversal of 21378842 is 24887312.

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

It can be written as a sum of positive squares in only one way, i.e., 21335161 + 43681 = 4619^2 + 209^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5344709 + ... + 5344712.

Almost surely, 2^21378842 is an apocalyptic number.

21378842 is a deficient number, since it is larger than the sum of its proper divisors (10689424).

21378842 is a wasteful number, since it uses less digits than its factorization.

21378842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10689423.

The product of its digits is 21504, while the sum is 35.

The square root of 21378842 is about 4623.7259866908. The cubic root of 21378842 is about 277.5415818434.

The spelling of 21378842 in words is "twenty-one million, three hundred seventy-eight thousand, eight hundred forty-two".