21967657 has 2 divisors, whose sum is σ = 21967658. Its totient is φ = 21967656.

The previous prime is 21967651. The next prime is 21967661. The reversal of 21967657 is 75676912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18011536 + 3956121 = 4244^2 + 1989^2 .

It is a cyclic number.

It is not a de Polignac number, because 21967657 - 2¹⁵ = 21934889 is a prime.

It is not a weakly prime, because it can be changed into another prime (21967651) 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, 10983828 + 10983829.

It is an arithmetic number, because the mean of its divisors is an integer number (10983829).

Almost surely, 2^21967657 is an apocalyptic number.

It is an amenable number.

21967657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21967657 is an equidigital number, since it uses as much as digits as its factorization.

21967657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 158760, while the sum is 43.

The square root of 21967657 is about 4686.9667163316. The cubic root of 21967657 is about 280.0665530573.

It can be divided in two parts, 219 and 67657, that added together give a palindrome (67876).

The spelling of 21967657 in words is "twenty-one million, nine hundred sixty-seven thousand, six hundred fifty-seven".