21161761 has 2 divisors, whose sum is σ = 21161762. Its totient is φ = 21161760.

The previous prime is 21161737. The next prime is 21161779. The reversal of 21161761 is 16716112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19088161 + 2073600 = 4369^2 + 1440^2 .

It is a cyclic number.

It is not a de Polignac number, because 21161761 - 2⁵ = 21161729 is a prime.

It is a super-2 number, since 2×21161761² = 895640257242242, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21161731) 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 as a sum of consecutive naturals, namely, 10580880 + 10580881.

It is an arithmetic number, because the mean of its divisors is an integer number (10580881).

Almost surely, 2^21161761 is an apocalyptic number.

It is an amenable number.

21161761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21161761 is an equidigital number, since it uses as much as digits as its factorization.

21161761 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 504, while the sum is 25.

The square root of 21161761 is about 4600.1914090611. The cubic root of 21161761 is about 276.5989974985.

Adding to 21161761 its reverse (16716112), we get a palindrome (37877873).

The spelling of 21161761 in words is "twenty-one million, one hundred sixty-one thousand, seven hundred sixty-one".