21478864 has 20 divisors (see below), whose sum is σ = 45398880. Its totient is φ = 9763040.

The previous prime is 21478861. The next prime is 21478867. The reversal of 21478864 is 46887412.

It is an interprime number because it is at equal distance from previous prime (21478861) and next prime (21478867).

It is a super-2 number, since 2×21478864² = 922683197460992, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21478861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60844 + ... + 61195.

It is an arithmetic number, because the mean of its divisors is an integer number (2269944).

Almost surely, 2^21478864 is an apocalyptic number.

It is an amenable number.

21478864 is an abundant number, since it is smaller than the sum of its proper divisors (23920016).

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

21478864 is a wasteful number, since it uses less digits than its factorization.

21478864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122058 (or 122052 counting only the distinct ones).

The product of its digits is 86016, while the sum is 40.

The square root of 21478864 is about 4634.5295338362. The cubic root of 21478864 is about 277.9737393892.

It can be divided in two parts, 2147 and 8864, that added together give a palindrome (11011).

The spelling of 21478864 in words is "twenty-one million, four hundred seventy-eight thousand, eight hundred sixty-four".