21366999 has 12 divisors (see below), whose sum is σ = 31520736. Its totient is φ = 13941312.

The previous prime is 21366973. The next prime is 21367009. The reversal of 21366999 is 99966312.

It is a happy number.

It is not a de Polignac number, because 21366999 - 2⁹ = 21366487 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365999) 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 11 ways as a sum of consecutive naturals, for example, 24834 + ... + 25679.

It is an arithmetic number, because the mean of its divisors is an integer number (2626728).

Almost surely, 2^21366999 is an apocalyptic number.

21366999 is a deficient number, since it is larger than the sum of its proper divisors (10153737).

21366999 is a wasteful number, since it uses less digits than its factorization.

21366999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50566 (or 50563 counting only the distinct ones).

The product of its digits is 157464, while the sum is 45.

The square root of 21366999 is about 4622.4451321784. The cubic root of 21366999 is about 277.4903234999.

The spelling of 21366999 in words is "twenty-one million, three hundred sixty-six thousand, nine hundred ninety-nine".