21339497 has 2 divisors, whose sum is σ = 21339498. Its totient is φ = 21339496.

The previous prime is 21339473. The next prime is 21339499. The reversal of 21339497 is 79493312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21307456 + 32041 = 4616^2 + 179^2 .

It is a cyclic number.

It is not a de Polignac number, because 21339497 - 2¹⁶ = 21273961 is a prime.

Together with 21339499, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21339497.

It is not a weakly prime, because it can be changed into another prime (21339499) 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 as a sum of consecutive naturals, namely, 10669748 + 10669749.

It is an arithmetic number, because the mean of its divisors is an integer number (10669749).

Almost surely, 2^21339497 is an apocalyptic number.

It is an amenable number.

21339497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21339497 is an equidigital number, since it uses as much as digits as its factorization.

21339497 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 40824, while the sum is 38.

The square root of 21339497 is about 4619.4693418184. The cubic root of 21339497 is about 277.3712174669.

The spelling of 21339497 in words is "twenty-one million, three hundred thirty-nine thousand, four hundred ninety-seven".