21378456 has 48 divisors (see below), whose sum is σ = 63165960. Its totient is φ = 6478080.

The previous prime is 21378443. The next prime is 21378457. The reversal of 21378456 is 65487312.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21378456.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12705 + ... + 14288.

Almost surely, 2^21378456 is an apocalyptic number.

It is an amenable number.

21378456 is an abundant number, since it is smaller than the sum of its proper divisors (41787504).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21378456 is a wasteful number, since it uses less digits than its factorization.

21378456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27016 (or 27009 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 21378456 is about 4623.6842452745. The cubic root of 21378456 is about 277.5399114740.

The spelling of 21378456 in words is "twenty-one million, three hundred seventy-eight thousand, four hundred fifty-six".