21666480 has 160 divisors (see below), whose sum is σ = 76066560. Its totient is φ = 5053440.

The previous prime is 21666443. The next prime is 21666481. The reversal of 21666480 is 8466612.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21666481) 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, 76419 + ... + 76701.

It is an arithmetic number, because the mean of its divisors is an integer number (475416).

Almost surely, 2^21666480 is an apocalyptic number.

21666480 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 21666480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38033280).

21666480 is an abundant number, since it is smaller than the sum of its proper divisors (54400080).

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

21666480 is a wasteful number, since it uses less digits than its factorization.

21666480 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339 (or 333 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 33.

The square root of 21666480 is about 4654.7266299967. The cubic root of 21666480 is about 278.7807529732.

It can be divided in two parts, 2166 and 6480, that added together give a triangular number (8646 = T₁₃₁).

The spelling of 21666480 in words is "twenty-one million, six hundred sixty-six thousand, four hundred eighty".