21666827 has 16 divisors (see below), whose sum is σ = 26776512. Its totient is φ = 17072640.

The previous prime is 21666817. The next prime is 21666829. The reversal of 21666827 is 72866612.

It is a happy number.

It is not a de Polignac number, because 21666827 - 2⁴ = 21666811 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21666829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41327 + ... + 41847.

It is an arithmetic number, because the mean of its divisors is an integer number (1673532).

Almost surely, 2^21666827 is an apocalyptic number.

21666827 is a deficient number, since it is larger than the sum of its proper divisors (5109685).

21666827 is a wasteful number, since it uses less digits than its factorization.

21666827 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 998.

The product of its digits is 48384, while the sum is 38.

The square root of 21666827 is about 4654.7639037872. The cubic root of 21666827 is about 278.7822412384.

The spelling of 21666827 in words is "twenty-one million, six hundred sixty-six thousand, eight hundred twenty-seven".