21478666 has 8 divisors (see below), whose sum is σ = 35146944. Its totient is φ = 9763020.

The previous prime is 21478663. The next prime is 21478669. The reversal of 21478666 is 66687412.

It is an interprime number because it is at equal distance from previous prime (21478663) and next prime (21478669).

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

It is a super-2 number, since 2×21478666² = 922666186279112, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21478661) by changing a digit.

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, 488130 + ... + 488173.

It is an arithmetic number, because the mean of its divisors is an integer number (4393368).

Almost surely, 2^21478666 is an apocalyptic number.

21478666 is a deficient number, since it is larger than the sum of its proper divisors (13668278).

21478666 is a wasteful number, since it uses less digits than its factorization.

21478666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 976316.

The product of its digits is 96768, while the sum is 40.

The square root of 21478666 is about 4634.5081723954. The cubic root of 21478666 is about 277.9728852322.

The spelling of 21478666 in words is "twenty-one million, four hundred seventy-eight thousand, six hundred sixty-six".