21478 has 4 divisors (see below), whose sum is σ = 32220. Its totient is φ = 10738.

The previous prime is 21467. The next prime is 21481. The reversal of 21478 is 87412.

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

It is a super-2 number, since 2×21478² = 922608968, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5368 + ... + 5371.

It is an arithmetic number, because the mean of its divisors is an integer number (8055).

2²¹⁴⁷⁸ is an apocalyptic number.

21478 is a deficient number, since it is larger than the sum of its proper divisors (10742).

21478 is a wasteful number, since it uses less digits than its factorization.

21478 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10741.

The product of its digits is 448, while the sum is 22.

The square root of 21478 is about 146.5537444080. The cubic root of 21478 is about 27.7970012120.

It can be divided in two parts, 214 and 78, that added together give a palindrome (292).

The spelling of 21478 in words is "twenty-one thousand, four hundred seventy-eight".