21136653 has 8 divisors (see below), whose sum is σ = 31313600. Its totient is φ = 14091084.

The previous prime is 21136649. The next prime is 21136663. The reversal of 21136653 is 35663112.

21136653 is a `hidden beast` number, since 2 + 1 + 1 + 3 + 6 + 653 = 666.

It is not a de Polignac number, because 21136653 - 2² = 21136649 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 782839 = 21136653 / (2 + 1 + 1 + 3 + 6 + 6 + 5 + 3).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21136603) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 391393 + ... + 391446.

It is an arithmetic number, because the mean of its divisors is an integer number (3914200).

Almost surely, 2^21136653 is an apocalyptic number.

It is an amenable number.

21136653 is a deficient number, since it is larger than the sum of its proper divisors (10176947).

21136653 is an equidigital number, since it uses as much as digits as its factorization.

21136653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 782848 (or 782842 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 21136653 is about 4597.4615822212. The cubic root of 21136653 is about 276.4895611732.

Adding to 21136653 its reverse (35663112), we get a palindrome (56799765).

It can be divided in two parts, 211 and 36653, that added together give a square (36864 = 192²).

The spelling of 21136653 in words is "twenty-one million, one hundred thirty-six thousand, six hundred fifty-three".