21741581 has 2 divisors, whose sum is σ = 21741582. Its totient is φ = 21741580.

The previous prime is 21741569. The next prime is 21741583. The reversal of 21741581 is 18514712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18966025 + 2775556 = 4355^2 + 1666^2 .

It is a cyclic number.

It is not a de Polignac number, because 21741581 - 2¹⁰ = 21740557 is a prime.

It is a super-2 number, since 2×21741581² = 945392688759122, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 21741583, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21741583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10870790 + 10870791.

It is an arithmetic number, because the mean of its divisors is an integer number (10870791).

Almost surely, 2^21741581 is an apocalyptic number.

It is an amenable number.

21741581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21741581 is an equidigital number, since it uses as much as digits as its factorization.

21741581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2240, while the sum is 29.

The square root of 21741581 is about 4662.7868276386. The cubic root of 21741581 is about 279.1024875808.

It can be divided in two parts, 21741 and 581, that added together give a palindrome (22322).

The spelling of 21741581 in words is "twenty-one million, seven hundred forty-one thousand, five hundred eighty-one".