21605677 has 2 divisors, whose sum is σ = 21605678. Its totient is φ = 21605676.

The previous prime is 21605663. The next prime is 21605693. The reversal of 21605677 is 77650612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20738916 + 866761 = 4554^2 + 931^2 .

It is a cyclic number.

It is not a de Polignac number, because 21605677 - 2¹⁵ = 21572909 is a prime.

It is equal to p_1365847 and since 21605677 and 1365847 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21605627) 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, 10802838 + 10802839.

It is an arithmetic number, because the mean of its divisors is an integer number (10802839).

Almost surely, 2^21605677 is an apocalyptic number.

It is an amenable number.

21605677 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605677 is an equidigital number, since it uses as much as digits as its factorization.

21605677 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17640, while the sum is 34.

The square root of 21605677 is about 4648.1907232815. The cubic root of 21605677 is about 278.5197263053.

The spelling of 21605677 in words is "twenty-one million, six hundred five thousand, six hundred seventy-seven".