21378267 has 24 divisors (see below), whose sum is σ = 32473584. Its totient is φ = 13535424.

The previous prime is 21378233. The next prime is 21378271. The reversal of 21378267 is 76287312.

21378267 is a `hidden beast` number, since 21 + 378 + 267 = 666.

It is not a de Polignac number, because 21378267 - 2⁷ = 21378139 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21378277) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13573 + ... + 15065.

It is an arithmetic number, because the mean of its divisors is an integer number (1353066).

Almost surely, 2^21378267 is an apocalyptic number.

21378267 is a deficient number, since it is larger than the sum of its proper divisors (11095317).

21378267 is a wasteful number, since it uses less digits than its factorization.

21378267 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1579 (or 1576 counting only the distinct ones).

The product of its digits is 28224, while the sum is 36.

The square root of 21378267 is about 4623.6638069825. The cubic root of 21378267 is about 277.5390935914.

It can be divided in two parts, 2137 and 8267, that added together give a square (10404 = 102²).

The spelling of 21378267 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred sixty-seven".