21639361 has 2 divisors, whose sum is σ = 21639362. Its totient is φ = 21639360.

The previous prime is 21639341. The next prime is 21639367. The reversal of 21639361 is 16393612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18326961 + 3312400 = 4281^2 + 1820^2 .

It is a cyclic number.

It is not a de Polignac number, because 21639361 - 2⁵ = 21639329 is a prime.

It is not a weakly prime, because it can be changed into another prime (21639367) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10819680 + 10819681.

It is an arithmetic number, because the mean of its divisors is an integer number (10819681).

Almost surely, 2^21639361 is an apocalyptic number.

It is an amenable number.

21639361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21639361 is an equidigital number, since it uses as much as digits as its factorization.

21639361 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5832, while the sum is 31.

The square root of 21639361 is about 4651.8126574487. The cubic root of 21639361 is about 278.6643917905.

The spelling of 21639361 in words is "twenty-one million, six hundred thirty-nine thousand, three hundred sixty-one".