21548551 has 2 divisors, whose sum is σ = 21548552. Its totient is φ = 21548550.

The previous prime is 21548531. The next prime is 21548561. The reversal of 21548551 is 15584512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21548551 is a prime.

It is a zygodrome in base 11.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21548531) 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, 10774275 + 10774276.

It is an arithmetic number, because the mean of its divisors is an integer number (10774276).

Almost surely, 2^21548551 is an apocalyptic number.

21548551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21548551 is an equidigital number, since it uses as much as digits as its factorization.

21548551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8000, while the sum is 31.

The square root of 21548551 is about 4642.0416844315. The cubic root of 21548551 is about 278.2740383887.

The spelling of 21548551 in words is "twenty-one million, five hundred forty-eight thousand, five hundred fifty-one".