21489739 has 2 divisors, whose sum is σ = 21489740. Its totient is φ = 21489738.

The previous prime is 21489737. The next prime is 21489761. The reversal of 21489739 is 93798412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21489739 - 2¹ = 21489737 is a prime.

Together with 21489737, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21489695 and 21489704.

It is not a weakly prime, because it can be changed into another prime (21489731) 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, 10744869 + 10744870.

It is an arithmetic number, because the mean of its divisors is an integer number (10744870).

Almost surely, 2^21489739 is an apocalyptic number.

21489739 is a deficient number, since it is larger than the sum of its proper divisors (1).

21489739 is an equidigital number, since it uses as much as digits as its factorization.

21489739 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 43.

The square root of 21489739 is about 4635.7026436129. The cubic root of 21489739 is about 278.0206452587.

The spelling of 21489739 in words is "twenty-one million, four hundred eighty-nine thousand, seven hundred thirty-nine".