21666010 has 8 divisors (see below), whose sum is σ = 38998836. Its totient is φ = 8666400.

The previous prime is 21665989. The next prime is 21666019. The reversal of 21666010 is 1066612.

It can be written as a sum of positive squares in 2 ways, for example, as 19070689 + 2595321 = 4367^2 + 1611^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21666019) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1083291 + ... + 1083310.

Almost surely, 2^21666010 is an apocalyptic number.

21666010 is a deficient number, since it is larger than the sum of its proper divisors (17332826).

21666010 is a wasteful number, since it uses less digits than its factorization.

21666010 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2166608.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21666010 is about 4654.6761434068. The cubic root of 21666010 is about 278.7787371420.

The spelling of 21666010 in words is "twenty-one million, six hundred sixty-six thousand, ten".