21320749 has 2 divisors, whose sum is σ = 21320750. Its totient is φ = 21320748.

The previous prime is 21320743. The next prime is 21320801. The reversal of 21320749 is 94702312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17280649 + 4040100 = 4157^2 + 2010^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320749 - 2²¹ = 19223597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21320743) 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 as a sum of consecutive naturals, namely, 10660374 + 10660375.

It is an arithmetic number, because the mean of its divisors is an integer number (10660375).

Almost surely, 2^21320749 is an apocalyptic number.

It is an amenable number.

21320749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320749 is an equidigital number, since it uses as much as digits as its factorization.

21320749 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21320749 is about 4617.4396585121. The cubic root of 21320749 is about 277.2899647049.

The spelling of 21320749 in words is "twenty-one million, three hundred twenty thousand, seven hundred forty-nine".