21135637 has 2 divisors, whose sum is σ = 21135638. Its totient is φ = 21135636.

The previous prime is 21135613. The next prime is 21135649. The reversal of 21135637 is 73653112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11655396 + 9480241 = 3414^2 + 3079^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135637 - 2¹¹ = 21133589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21135677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10567818 + 10567819.

It is an arithmetic number, because the mean of its divisors is an integer number (10567819).

Almost surely, 2^21135637 is an apocalyptic number.

It is an amenable number.

21135637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135637 is an equidigital number, since it uses as much as digits as its factorization.

21135637 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3780, while the sum is 28.

The square root of 21135637 is about 4597.3510851359. The cubic root of 21135637 is about 276.4851309875.

Adding to 21135637 its reverse (73653112), we get a palindrome (94788749).

It can be divided in two parts, 2113 and 5637, that added together give a triangular number (7750 = T₁₂₄).

The spelling of 21135637 in words is "twenty-one million, one hundred thirty-five thousand, six hundred thirty-seven".