21478851 has 20 divisors (see below), whose sum is σ = 32233432. Its totient is φ = 14253408.

The previous prime is 21478841. The next prime is 21478861. The reversal of 21478851 is 15887412.

It is an interprime number because it is at equal distance from previous prime (21478841) and next prime (21478861).

It is not a de Polignac number, because 21478851 - 2⁹ = 21478339 is a prime.

It is a super-2 number, since 2×21478851² = 922682080560402, which contains 22 as substring.

It is a Duffinian number.

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

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 22455 + ... + 23391.

Almost surely, 2^21478851 is an apocalyptic number.

21478851 is a deficient number, since it is larger than the sum of its proper divisors (10754581).

21478851 is an equidigital number, since it uses as much as digits as its factorization.

21478851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1232 (or 1223 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 21478851 is about 4634.5281313204. The cubic root of 21478851 is about 277.9736833084.

The spelling of 21478851 in words is "twenty-one million, four hundred seventy-eight thousand, eight hundred fifty-one".