21673440 has 192 divisors, whose sum is σ = 78926400. Its totient is φ = 5548032.

The previous prime is 21673423. The next prime is 21673459. The reversal of 21673440 is 4437612.

21673440 is a `hidden beast` number, since 216 + 7 + 3 + 440 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

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, 125194 + ... + 125366.

It is an arithmetic number, because the mean of its divisors is an integer number (411075).

Almost surely, 2^21673440 is an apocalyptic number.

21673440 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 21673440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39463200).

21673440 is an abundant number, since it is smaller than the sum of its proper divisors (57252960).

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

21673440 is a wasteful number, since it uses less digits than its factorization.

21673440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226 (or 212 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 27.

The square root of 21673440 is about 4655.4741971146. The cubic root of 21673440 is about 278.8106010198.

The spelling of 21673440 in words is "twenty-one million, six hundred seventy-three thousand, four hundred forty".