21831864 has 32 divisors (see below), whose sum is σ = 54712320. Its totient is φ = 7259616.

The previous prime is 21831863. The next prime is 21831869. The reversal of 21831864 is 46813812.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21831863) 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, 12297 + ... + 13959.

It is an arithmetic number, because the mean of its divisors is an integer number (1709760).

Almost surely, 2^21831864 is an apocalyptic number.

21831864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21831864 is an abundant number, since it is smaller than the sum of its proper divisors (32880456).

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

21831864 is a wasteful number, since it uses less digits than its factorization.

21831864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2219 (or 2215 counting only the distinct ones).

The product of its digits is 9216, while the sum is 33.

The square root of 21831864 is about 4672.4580254936. The cubic root of 21831864 is about 279.4882830631.

The spelling of 21831864 in words is "twenty-one million, eight hundred thirty-one thousand, eight hundred sixty-four".