21066651 has 6 divisors (see below), whose sum is σ = 30429620. Its totient is φ = 14044428.

The previous prime is 21066641. The next prime is 21066677. The reversal of 21066651 is 15666012.

It is a happy number.

It is not a de Polignac number, because 21066651 - 2⁷ = 21066523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21066601) 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 5 ways as a sum of consecutive naturals, for example, 1170361 + ... + 1170378.

Almost surely, 2^21066651 is an apocalyptic number.

21066651 is a deficient number, since it is larger than the sum of its proper divisors (9362969).

21066651 is a wasteful number, since it uses less digits than its factorization.

21066651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2340745 (or 2340742 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21066651 is about 4589.8421541487. The cubic root of 21066651 is about 276.1839904253.

The spelling of 21066651 in words is "twenty-one million, sixty-six thousand, six hundred fifty-one".