21091361 has 2 divisors, whose sum is σ = 21091362. Its totient is φ = 21091360.

The previous prime is 21091351. The next prime is 21091409. The reversal of 21091361 is 16319012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16443025 + 4648336 = 4055^2 + 2156^2 .

It is a cyclic number.

It is not a de Polignac number, because 21091361 - 2¹⁸ = 20829217 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21091351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10545680 + 10545681.

It is an arithmetic number, because the mean of its divisors is an integer number (10545681).

Almost surely, 2^21091361 is an apocalyptic number.

It is an amenable number.

21091361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21091361 is an equidigital number, since it uses as much as digits as its factorization.

21091361 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 21091361 is about 4592.5331789765. The cubic root of 21091361 is about 276.2919310101.

The spelling of 21091361 in words is "twenty-one million, ninety-one thousand, three hundred sixty-one".