21478871 has 4 divisors (see below), whose sum is σ = 22742352. Its totient is φ = 20215392.

The previous prime is 21478867. The next prime is 21478883. The reversal of 21478871 is 17887412.

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

It is a cyclic number.

It is not a de Polignac number, because 21478871 - 2² = 21478867 is a prime.

It is a super-2 number, since 2×21478871² = 922683798869282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21478841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 631715 + ... + 631748.

It is an arithmetic number, because the mean of its divisors is an integer number (5685588).

Almost surely, 2^21478871 is an apocalyptic number.

21478871 is a deficient number, since it is larger than the sum of its proper divisors (1263481).

21478871 is a wasteful number, since it uses less digits than its factorization.

21478871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1263480.

The product of its digits is 25088, while the sum is 38.

The square root of 21478871 is about 4634.5302890369. The cubic root of 21478871 is about 277.9737695866.

The spelling of 21478871 in words is "twenty-one million, four hundred seventy-eight thousand, eight hundred seventy-one".