21693840 has 160 divisors (see below), whose sum is σ = 79161600. Its totient is φ = 4810752.

The previous prime is 21693823. The next prime is 21693851. The reversal of 21693840 is 4839612.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 61986 + ... + 62334.

It is an arithmetic number, because the mean of its divisors is an integer number (494760).

Almost surely, 2^21693840 is an apocalyptic number.

21693840 is a gapful number since it is divisible by the number (20) 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 21693840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39580800).

21693840 is an abundant number, since it is smaller than the sum of its proper divisors (57467760).

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

21693840 is a wasteful number, since it uses less digits than its factorization.

21693840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 409 (or 403 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 21693840 is about 4657.6646508739. The cubic root of 21693840 is about 278.8980498770.

The spelling of 21693840 in words is "twenty-one million, six hundred ninety-three thousand, eight hundred forty".