21240999 has 24 divisors (see below), whose sum is σ = 33520032. Its totient is φ = 12882240.

The previous prime is 21240991. The next prime is 21241013. The reversal of 21240999 is 99904212.

It is not a de Polignac number, because 21240999 - 2³ = 21240991 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240991) 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 23 ways as a sum of consecutive naturals, for example, 7029 + ... + 9585.

It is an arithmetic number, because the mean of its divisors is an integer number (1396668).

Almost surely, 2^21240999 is an apocalyptic number.

21240999 is a deficient number, since it is larger than the sum of its proper divisors (12279033).

21240999 is a wasteful number, since it uses less digits than its factorization.

21240999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2647 (or 2644 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 21240999 is about 4608.7958297152. The cubic root of 21240999 is about 276.9437994998.

The spelling of 21240999 in words is "twenty-one million, two hundred forty thousand, nine hundred ninety-nine".