21135555 has 48 divisors (see below), whose sum is σ = 42194880. Its totient is φ = 9586944.

The previous prime is 21135553. The next prime is 21135559. The reversal of 21135555 is 55553112.

It is not a de Polignac number, because 21135555 - 2¹ = 21135553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21135553) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 71989 + ... + 72281.

It is an arithmetic number, because the mean of its divisors is an integer number (879060).

Almost surely, 2^21135555 is an apocalyptic number.

21135555 is a deficient number, since it is larger than the sum of its proper divisors (21059325).

21135555 is a wasteful number, since it uses less digits than its factorization.

21135555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 540 (or 537 counting only the distinct ones).

The product of its digits is 3750, while the sum is 27.

The square root of 21135555 is about 4597.3421669482. The cubic root of 21135555 is about 276.4847734269.

Adding to 21135555 its reverse (55553112), we get a palindrome (76688667).

The spelling of 21135555 in words is "twenty-one million, one hundred thirty-five thousand, five hundred fifty-five".