21147864 has 48 divisors (see below), whose sum is σ = 56181000. Its totient is φ = 6632448.

The previous prime is 21147851. The next prime is 21147869. The reversal of 21147864 is 46874112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147869) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5412 + ... + 8460.

Almost surely, 2^21147864 is an apocalyptic number.

21147864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21147864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28090500).

21147864 is an abundant number, since it is smaller than the sum of its proper divisors (35033136).

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

21147864 is a wasteful number, since it uses less digits than its factorization.

21147864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3092 (or 3071 counting only the distinct ones).

The product of its digits is 10752, while the sum is 33.

The square root of 21147864 is about 4598.6806803691. The cubic root of 21147864 is about 276.5384364074.

The spelling of 21147864 in words is "twenty-one million, one hundred forty-seven thousand, eight hundred sixty-four".