21545455 has 8 divisors (see below), whose sum is σ = 25880400. Its totient is φ = 17219136.

The previous prime is 21545441. The next prime is 21545471. The reversal of 21545455 is 55454512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21545455 - 2⁷ = 21545327 is a prime.

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 6531 + ... + 9259.

It is an arithmetic number, because the mean of its divisors is an integer number (3235050).

Almost surely, 2^21545455 is an apocalyptic number.

21545455 is a deficient number, since it is larger than the sum of its proper divisors (4334945).

21545455 is a wasteful number, since it uses less digits than its factorization.

21545455 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4313.

The product of its digits is 20000, while the sum is 31.

The square root of 21545455 is about 4641.7081984976. The cubic root of 21545455 is about 278.2607106915.

Adding to 21545455 its reverse (55454512), we get a palindrome (76999967).

The spelling of 21545455 in words is "twenty-one million, five hundred forty-five thousand, four hundred fifty-five".