21682709 has 2 divisors, whose sum is σ = 21682710. Its totient is φ = 21682708.

The previous prime is 21682699. The next prime is 21682757. The reversal of 21682709 is 90728612.

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., 20295025 + 1387684 = 4505^2 + 1178^2 .

It is a cyclic number.

It is not a de Polignac number, because 21682709 - 2⁴ = 21682693 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21682109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10841354 + 10841355.

It is an arithmetic number, because the mean of its divisors is an integer number (10841355).

Almost surely, 2^21682709 is an apocalyptic number.

It is an amenable number.

21682709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21682709 is an equidigital number, since it uses as much as digits as its factorization.

21682709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 21682709 is about 4656.4695854263. The cubic root of 21682709 is about 278.8503413217.

The spelling of 21682709 in words is "twenty-one million, six hundred eighty-two thousand, seven hundred nine".