21530749 has 2 divisors, whose sum is σ = 21530750. Its totient is φ = 21530748.

The previous prime is 21530741. The next prime is 21530777. The reversal of 21530749 is 94703512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21483225 + 47524 = 4635^2 + 218^2 .

It is a cyclic number.

It is not a de Polignac number, because 21530749 - 2³ = 21530741 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21530749.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21530741) 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, 10765374 + 10765375.

It is an arithmetic number, because the mean of its divisors is an integer number (10765375).

Almost surely, 2^21530749 is an apocalyptic number.

It is an amenable number.

21530749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21530749 is an equidigital number, since it uses as much as digits as its factorization.

21530749 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7560, while the sum is 31.

The square root of 21530749 is about 4640.1238130033. The cubic root of 21530749 is about 278.1973866881.

The spelling of 21530749 in words is "twenty-one million, five hundred thirty thousand, seven hundred forty-nine".