21135641 has 4 divisors (see below), whose sum is σ = 22378932. Its totient is φ = 19892352.

The previous prime is 21135637. The next prime is 21135649. The reversal of 21135641 is 14653112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10272025 + 10863616 = 3205^2 + 3296^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135641 - 2² = 21135637 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21135649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 621620 + ... + 621653.

It is an arithmetic number, because the mean of its divisors is an integer number (5594733).

Almost surely, 2^21135641 is an apocalyptic number.

It is an amenable number.

21135641 is a deficient number, since it is larger than the sum of its proper divisors (1243291).

21135641 is a wasteful number, since it uses less digits than its factorization.

21135641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1243290.

The product of its digits is 720, while the sum is 23.

The square root of 21135641 is about 4597.3515201690. The cubic root of 21135641 is about 276.4851484294.

Adding to 21135641 its reverse (14653112), we get a palindrome (35788753).

The spelling of 21135641 in words is "twenty-one million, one hundred thirty-five thousand, six hundred forty-one".