21135761 has 2 divisors, whose sum is σ = 21135762. Its totient is φ = 21135760.

The previous prime is 21135731. The next prime is 21135767. The reversal of 21135761 is 16753112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15523600 + 5612161 = 3940^2 + 2369^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135761 - 2¹⁴ = 21119377 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21135761.

It is not a weakly prime, because it can be changed into another prime (21135767) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10567880 + 10567881.

It is an arithmetic number, because the mean of its divisors is an integer number (10567881).

Almost surely, 2^21135761 is an apocalyptic number.

It is an amenable number.

21135761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135761 is an equidigital number, since it uses as much as digits as its factorization.

21135761 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1260, while the sum is 26.

The square root of 21135761 is about 4597.3645711429. The cubic root of 21135761 is about 276.4856716870.

Adding to 21135761 its reverse (16753112), we get a palindrome (37888873).

The spelling of 21135761 in words is "twenty-one million, one hundred thirty-five thousand, seven hundred sixty-one".