21963864 has 128 divisors (see below), whose sum is σ = 64774080. Its totient is φ = 6144000.

The previous prime is 21963863. The next prime is 21963869. The reversal of 21963864 is 46836912.

It is a super-2 number, since 2×21963864² = 964822643620992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21963863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 217414 + ... + 217514.

Almost surely, 2^21963864 is an apocalyptic number.

21963864 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 21963864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32387040).

21963864 is an abundant number, since it is smaller than the sum of its proper divisors (42810216).

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

21963864 is a wasteful number, since it uses less digits than its factorization.

21963864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 181 (or 177 counting only the distinct ones).

The product of its digits is 62208, while the sum is 39.

The square root of 21963864 is about 4686.5620661632. The cubic root of 21963864 is about 280.0504330924.

The spelling of 21963864 in words is "twenty-one million, nine hundred sixty-three thousand, eight hundred sixty-four".