21406478 has 4 divisors (see below), whose sum is σ = 32109720. Its totient is φ = 10703238.

The previous prime is 21406471. The next prime is 21406481. The reversal of 21406478 is 87460412.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21406471) 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 as a sum of consecutive naturals, namely, 5351618 + ... + 5351621.

It is an arithmetic number, because the mean of its divisors is an integer number (8027430).

Almost surely, 2^21406478 is an apocalyptic number.

21406478 is a deficient number, since it is larger than the sum of its proper divisors (10703242).

21406478 is a wasteful number, since it uses less digits than its factorization.

21406478 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10703241.

The product of its (nonzero) digits is 10752, while the sum is 32.

The square root of 21406478 is about 4626.7135204160. The cubic root of 21406478 is about 277.6611211605.

The spelling of 21406478 in words is "twenty-one million, four hundred six thousand, four hundred seventy-eight".