21387278 has 16 divisors (see below), whose sum is σ = 35199360. Its totient is φ = 9665400.

The previous prime is 21387277. The next prime is 21387287. The reversal of 21387278 is 87278312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387277) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1223 + ... + 6653.

It is an arithmetic number, because the mean of its divisors is an integer number (2199960).

Almost surely, 2^21387278 is an apocalyptic number.

21387278 is a deficient number, since it is larger than the sum of its proper divisors (13812082).

21387278 is a wasteful number, since it uses less digits than its factorization.

21387278 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5623.

The product of its digits is 37632, while the sum is 38.

The square root of 21387278 is about 4624.6381480068. The cubic root of 21387278 is about 277.5780826182.

The spelling of 21387278 in words is "twenty-one million, three hundred eighty-seven thousand, two hundred seventy-eight".