21101553 has 30 divisors (see below), whose sum is σ = 34664322. Its totient is φ = 12782880.

The previous prime is 21101551. The next prime is 21101569. The reversal of 21101553 is 35510112.

21101553 is a `hidden beast` number, since 2 + 110 + 1 + 553 = 666.

It can be written as a sum of positive squares in only one way, i.e., 13417569 + 7683984 = 3663^2 + 2772^2 .

It is not a de Polignac number, because 21101553 - 2¹ = 21101551 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21101551) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 8725 + ... + 10877.

Almost surely, 2^21101553 is an apocalyptic number.

It is an amenable number.

21101553 is a deficient number, since it is larger than the sum of its proper divisors (13562769).

21101553 is a wasteful number, since it uses less digits than its factorization.

21101553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2187 (or 2167 counting only the distinct ones).

The product of its (nonzero) digits is 150, while the sum is 18.

The square root of 21101553 is about 4593.6426722156. The cubic root of 21101553 is about 276.3364281211.

Adding to 21101553 its reverse (35510112), we get a palindrome (56611665).

It can be divided in two parts, 2110 and 1553, that added together give a palindrome (3663).

The spelling of 21101553 in words is "twenty-one million, one hundred one thousand, five hundred fifty-three".