21666426 has 8 divisors (see below), whose sum is σ = 43332864. Its totient is φ = 7222140.

The previous prime is 21666397. The next prime is 21666443. The reversal of 21666426 is 62466612.

It is a sphenic number, since it is the product of 3 distinct primes.

21666426 is an admirable number.

It is a super-2 number, since 2×21666426² = 938868031226952, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1805530 + ... + 1805541.

It is an arithmetic number, because the mean of its divisors is an integer number (5416608).

Almost surely, 2^21666426 is an apocalyptic number.

21666426 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21666426 is a wasteful number, since it uses less digits than its factorization.

21666426 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3611076.

The product of its digits is 20736, while the sum is 33.

The square root of 21666426 is about 4654.7208294376. The cubic root of 21666426 is about 278.7805213686.

The spelling of 21666426 in words is "twenty-one million, six hundred sixty-six thousand, four hundred twenty-six".