21435551 has 2 divisors, whose sum is σ = 21435552. Its totient is φ = 21435550.

The previous prime is 21435529. The next prime is 21435571. The reversal of 21435551 is 15553412.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21435551 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21435551.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21435571) 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, 10717775 + 10717776.

It is an arithmetic number, because the mean of its divisors is an integer number (10717776).

Almost surely, 2^21435551 is an apocalyptic number.

21435551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21435551 is an equidigital number, since it uses as much as digits as its factorization.

21435551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3000, while the sum is 26.

The square root of 21435551 is about 4629.8543173625. The cubic root of 21435551 is about 277.7867652144.

Adding to 21435551 its reverse (15553412), we get a palindrome (36988963).

The spelling of 21435551 in words is "twenty-one million, four hundred thirty-five thousand, five hundred fifty-one".