21682109 has 2 divisors, whose sum is σ = 21682110. Its totient is φ = 21682108.

The previous prime is 21682099. The next prime is 21682139. The reversal of 21682109 is 90128612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21362884 + 319225 = 4622^2 + 565^2 .

It is a cyclic number.

It is not a de Polignac number, because 21682109 - 2⁴ = 21682093 is a prime.

It is a super-2 number, since 2×21682109² = 940227701375762, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21682139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10841054 + 10841055.

It is an arithmetic number, because the mean of its divisors is an integer number (10841055).

Almost surely, 2^21682109 is an apocalyptic number.

It is an amenable number.

21682109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21682109 is an equidigital number, since it uses as much as digits as its factorization.

21682109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21682109 is about 4656.4051584887. The cubic root of 21682109 is about 278.8477691992.

The spelling of 21682109 in words is "twenty-one million, six hundred eighty-two thousand, one hundred nine".