21980657 has 2 divisors, whose sum is σ = 21980658. Its totient is φ = 21980656.

The previous prime is 21980653. The next prime is 21980659. The reversal of 21980657 is 75608912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21893041 + 87616 = 4679^2 + 296^2 .

It is a cyclic number.

It is not a de Polignac number, because 21980657 - 2² = 21980653 is a prime.

Together with 21980659, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21980657.

It is not a weakly prime, because it can be changed into another prime (21980653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10990328 + 10990329.

It is an arithmetic number, because the mean of its divisors is an integer number (10990329).

Almost surely, 2^21980657 is an apocalyptic number.

It is an amenable number.

21980657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21980657 is an equidigital number, since it uses as much as digits as its factorization.

21980657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 21980657 is about 4688.3533356606. The cubic root of 21980657 is about 280.1217880061.

The spelling of 21980657 in words is "twenty-one million, nine hundred eighty thousand, six hundred fifty-seven".