21135851 has 8 divisors (see below), whose sum is σ = 23098608. Its totient is φ = 19180000.

The previous prime is 21135841. The next prime is 21135857. The reversal of 21135851 is 15853112.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21135851 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21135851.

It is not an unprimeable number, because it can be changed into a prime (21135857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6341 + ... + 9081.

It is an arithmetic number, because the mean of its divisors is an integer number (2887326).

Almost surely, 2^21135851 is an apocalyptic number.

21135851 is a deficient number, since it is larger than the sum of its proper divisors (1962757).

21135851 is a wasteful number, since it uses less digits than its factorization.

21135851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3453.

The product of its digits is 1200, while the sum is 26.

The square root of 21135851 is about 4597.3743593490. The cubic root of 21135851 is about 276.4860641289.

Adding to 21135851 its reverse (15853112), we get a palindrome (36988963).

The spelling of 21135851 in words is "twenty-one million, one hundred thirty-five thousand, eight hundred fifty-one".