21026549 has 2 divisors, whose sum is σ = 21026550. Its totient is φ = 21026548.

The previous prime is 21026519. The next prime is 21026557. The reversal of 21026549 is 94562012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17098225 + 3928324 = 4135^2 + 1982^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21026549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21026519) 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, 10513274 + 10513275.

It is an arithmetic number, because the mean of its divisors is an integer number (10513275).

Almost surely, 2^21026549 is an apocalyptic number.

It is an amenable number.

21026549 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026549 is an equidigital number, since it uses as much as digits as its factorization.

21026549 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 21026549 is about 4585.4715133779. The cubic root of 21026549 is about 276.0086332453.

The spelling of 21026549 in words is "twenty-one million, twenty-six thousand, five hundred forty-nine".