21533215455 has 24 divisors (see below), whose sum is σ = 37338219360. Its totient is φ = 11480080320.

The previous prime is 21533215439. The next prime is 21533215481. The reversal of 21533215455 is 55451233512.

21533215455 is a `hidden beast` number, since 2 + 1 + 533 + 21 + 54 + 55 = 666.

It is not a de Polignac number, because 21533215455 - 2⁴ = 21533215439 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33741 + ... + 210249.

It is an arithmetic number, because the mean of its divisors is an integer number (1555759140).

Almost surely, 2^21533215455 is an apocalyptic number.

21533215455 is a deficient number, since it is larger than the sum of its proper divisors (15805003905).

21533215455 is a wasteful number, since it uses less digits than its factorization.

21533215455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179231 (or 179228 counting only the distinct ones).

The product of its digits is 90000, while the sum is 36.

Adding to 21533215455 its reverse (55451233512), we get a palindrome (76984448967).

The spelling of 21533215455 in words is "twenty-one billion, five hundred thirty-three million, two hundred fifteen thousand, four hundred fifty-five".