21428549 has 2 divisors, whose sum is σ = 21428550. Its totient is φ = 21428548.

The previous prime is 21428531. The next prime is 21428579. The reversal of 21428549 is 94582412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19624900 + 1803649 = 4430^2 + 1343^2 .

It is a cyclic number.

It is not a de Polignac number, because 21428549 - 2²⁰ = 20379973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21428509) 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, 10714274 + 10714275.

It is an arithmetic number, because the mean of its divisors is an integer number (10714275).

Almost surely, 2^21428549 is an apocalyptic number.

It is an amenable number.

21428549 is a deficient number, since it is larger than the sum of its proper divisors (1).

21428549 is an equidigital number, since it uses as much as digits as its factorization.

21428549 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23040, while the sum is 35.

The square root of 21428549 is about 4629.0980762995. The cubic root of 21428549 is about 277.7565152377.

The spelling of 21428549 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred forty-nine".