21221693 has 2 divisors, whose sum is σ = 21221694. Its totient is φ = 21221692.

The previous prime is 21221671. The next prime is 21221731. The reversal of 21221693 is 39612212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21141604 + 80089 = 4598^2 + 283^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221693 - 2¹² = 21217597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610846 + 10610847.

It is an arithmetic number, because the mean of its divisors is an integer number (10610847).

Almost surely, 2^21221693 is an apocalyptic number.

It is an amenable number.

21221693 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221693 is an equidigital number, since it uses as much as digits as its factorization.

21221693 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 26.

The square root of 21221693 is about 4606.7008802396. The cubic root of 21221693 is about 276.8598690833.

The spelling of 21221693 in words is "twenty-one million, two hundred twenty-one thousand, six hundred ninety-three".