21543499 has 2 divisors, whose sum is σ = 21543500. Its totient is φ = 21543498.

The previous prime is 21543461. The next prime is 21543503. The reversal of 21543499 is 99434512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21543499 - 2⁷ = 21543371 is a prime.

It is not a weakly prime, because it can be changed into another prime (21543439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771749 + 10771750.

It is an arithmetic number, because the mean of its divisors is an integer number (10771750).

Almost surely, 2^21543499 is an apocalyptic number.

21543499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21543499 is an equidigital number, since it uses as much as digits as its factorization.

21543499 is an evil number, because the sum of its binary digits is even.

The product of its digits is 38880, while the sum is 37.

The square root of 21543499 is about 4641.4974954211. The cubic root of 21543499 is about 278.2522898216.

The spelling of 21543499 in words is "twenty-one million, five hundred forty-three thousand, four hundred ninety-nine".