21623866 has 8 divisors (see below), whose sum is σ = 35384544. Its totient is φ = 9829020.

The previous prime is 21623857. The next prime is 21623867. The reversal of 21623866 is 66832612.

It is a happy number.

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

It is a super-3 number, since 3×21623866³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21623867) 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, 491430 + ... + 491473.

It is an arithmetic number, because the mean of its divisors is an integer number (4423068).

Almost surely, 2^21623866 is an apocalyptic number.

21623866 is a deficient number, since it is larger than the sum of its proper divisors (13760678).

21623866 is a wasteful number, since it uses less digits than its factorization.

21623866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 982916.

The product of its digits is 20736, while the sum is 34.

The square root of 21623866 is about 4650.1468794007. The cubic root of 21623866 is about 278.5978627807.

The spelling of 21623866 in words is "twenty-one million, six hundred twenty-three thousand, eight hundred sixty-six".