20783221 has 2 divisors, whose sum is σ = 20783222. Its totient is φ = 20783220.

The previous prime is 20783179. The next prime is 20783239. The reversal of 20783221 is 12238702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13950225 + 6832996 = 3735^2 + 2614^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20783221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20783291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10391610 + 10391611.

It is an arithmetic number, because the mean of its divisors is an integer number (10391611).

Almost surely, 2^20783221 is an apocalyptic number.

It is an amenable number.

20783221 is a deficient number, since it is larger than the sum of its proper divisors (1).

20783221 is an equidigital number, since it uses as much as digits as its factorization.

20783221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 20783221 is about 4558.8618097065. The cubic root of 20783221 is about 274.9398039042.

The spelling of 20783221 in words is "twenty million, seven hundred eighty-three thousand, two hundred twenty-one".