21786464 has 48 divisors (see below), whose sum is σ = 51609600. Its totient is φ = 8843904.

The previous prime is 21786461. The next prime is 21786467. The reversal of 21786464 is 46468712.

It is an interprime number because it is at equal distance from previous prime (21786461) and next prime (21786467).

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21786461) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1697 + ... + 6815.

It is an arithmetic number, because the mean of its divisors is an integer number (1075200).

Almost surely, 2^21786464 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21786464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25804800).

21786464 is an abundant number, since it is smaller than the sum of its proper divisors (29823136).

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

21786464 is a wasteful number, since it uses less digits than its factorization.

21786464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5155 (or 5147 counting only the distinct ones).

The product of its digits is 64512, while the sum is 38.

The square root of 21786464 is about 4667.5972405511. The cubic root of 21786464 is about 279.2944139279.

The spelling of 21786464 in words is "twenty-one million, seven hundred eighty-six thousand, four hundred sixty-four".