21891761 has 2 divisors, whose sum is σ = 21891762. Its totient is φ = 21891760.

The previous prime is 21891757. The next prime is 21891787. The reversal of 21891761 is 16719812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18447025 + 3444736 = 4295^2 + 1856^2 .

It is a cyclic number.

It is not a de Polignac number, because 21891761 - 2² = 21891757 is a prime.

It is a super-2 number, since 2×21891761² = 958498399362242, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21891061) 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, 10945880 + 10945881.

It is an arithmetic number, because the mean of its divisors is an integer number (10945881).

Almost surely, 2^21891761 is an apocalyptic number.

It is an amenable number.

21891761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21891761 is an equidigital number, since it uses as much as digits as its factorization.

21891761 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6048, while the sum is 35.

The square root of 21891761 is about 4678.8632166371. The cubic root of 21891761 is about 279.7436471716.

The spelling of 21891761 in words is "twenty-one million, eight hundred ninety-one thousand, seven hundred sixty-one".