21522749 has 2 divisors, whose sum is σ = 21522750. Its totient is φ = 21522748.

The previous prime is 21522737. The next prime is 21522791. The reversal of 21522749 is 94722512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21436900 + 85849 = 4630^2 + 293^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21522749 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21522719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10761374 + 10761375.

It is an arithmetic number, because the mean of its divisors is an integer number (10761375).

Almost surely, 2^21522749 is an apocalyptic number.

It is an amenable number.

21522749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21522749 is an equidigital number, since it uses as much as digits as its factorization.

21522749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10080, while the sum is 32.

The square root of 21522749 is about 4639.2616869498. The cubic root of 21522749 is about 278.1629265958.

The spelling of 21522749 in words is "twenty-one million, five hundred twenty-two thousand, seven hundred forty-nine".