21652681 has 2 divisors, whose sum is σ = 21652682. Its totient is φ = 21652680.

The previous prime is 21652661. The next prime is 21652691. The reversal of 21652681 is 18625612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18412681 + 3240000 = 4291^2 + 1800^2 .

It is a cyclic number.

It is not a de Polignac number, because 21652681 - 2¹³ = 21644489 is a prime.

It is a super-2 number, since 2×21652681² = 937677188975522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21652661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10826340 + 10826341.

It is an arithmetic number, because the mean of its divisors is an integer number (10826341).

Almost surely, 2^21652681 is an apocalyptic number.

It is an amenable number.

21652681 is a deficient number, since it is larger than the sum of its proper divisors (1).

21652681 is an equidigital number, since it uses as much as digits as its factorization.

21652681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5760, while the sum is 31.

The square root of 21652681 is about 4653.2441371585. The cubic root of 21652681 is about 278.7215568852.

The spelling of 21652681 in words is "twenty-one million, six hundred fifty-two thousand, six hundred eighty-one".