21378685 has 8 divisors (see below), whose sum is σ = 26482176. Its totient is φ = 16551120.

The previous prime is 21378683. The next prime is 21378691. The reversal of 21378685 is 58687312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21378685 - 2¹ = 21378683 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 (21378683) 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, 68809 + ... + 69118.

It is an arithmetic number, because the mean of its divisors is an integer number (3310272).

Almost surely, 2^21378685 is an apocalyptic number.

It is an amenable number.

21378685 is a deficient number, since it is larger than the sum of its proper divisors (5103491).

21378685 is a wasteful number, since it uses less digits than its factorization.

21378685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137963.

The product of its digits is 80640, while the sum is 40.

The square root of 21378685 is about 4623.7090090100. The cubic root of 21378685 is about 277.5409024469.

The spelling of 21378685 in words is "twenty-one million, three hundred seventy-eight thousand, six hundred eighty-five".