21378687 has 8 divisors (see below), whose sum is σ = 31096320. Its totient is φ = 12956760.

The previous prime is 21378683. The next prime is 21378691. The reversal of 21378687 is 78687312.

It is an interprime number because it is at equal distance from previous prime (21378683) and next prime (21378691).

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

It is not a de Polignac number, because 21378687 - 2² = 21378683 is a prime.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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, 323887 + ... + 323952.

It is an arithmetic number, because the mean of its divisors is an integer number (3887040).

Almost surely, 2^21378687 is an apocalyptic number.

21378687 is a deficient number, since it is larger than the sum of its proper divisors (9717633).

21378687 is a wasteful number, since it uses less digits than its factorization.

21378687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 647853.

The product of its digits is 112896, while the sum is 42.

The square root of 21378687 is about 4623.7092252866. The cubic root of 21378687 is about 277.5409111016.

The spelling of 21378687 in words is "twenty-one million, three hundred seventy-eight thousand, six hundred eighty-seven".