21378207 has 4 divisors (see below), whose sum is σ = 28504280. Its totient is φ = 14252136.

The previous prime is 21378187. The next prime is 21378209. The reversal of 21378207 is 70287312.

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

It is not a de Polignac number, because 21378207 - 2⁶ = 21378143 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378209) 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 3 ways as a sum of consecutive naturals, for example, 3563032 + ... + 3563037.

It is an arithmetic number, because the mean of its divisors is an integer number (7126070).

Almost surely, 2^21378207 is an apocalyptic number.

21378207 is a deficient number, since it is larger than the sum of its proper divisors (7126073).

21378207 is an equidigital number, since it uses as much as digits as its factorization.

21378207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7126072.

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 21378207 is about 4623.6573186169. The cubic root of 21378207 is about 277.5388339452.

The spelling of 21378207 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred seven".