2820205721 has 2 divisors, whose sum is σ = 2820205722. Its totient is φ = 2820205720.

The previous prime is 2820205669. The next prime is 2820205747. The reversal of 2820205721 is 1275020282.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2012509321 + 807696400 = 44861^2 + 28420^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2820205721 is a prime.

It is a super-2 number, since 2×2820205721² = 15907120617522259682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (2820205781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1410102860 + 1410102861.

It is an arithmetic number, because the mean of its divisors is an integer number (1410102861).

Almost surely, 2^2820205721 is an apocalyptic number.

It is an amenable number.

2820205721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2820205721 is an equidigital number, since it uses as much as digits as its factorization.

2820205721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4480, while the sum is 29.

The square root of 2820205721 is about 53105.6091293566. The cubic root of 2820205721 is about 1412.8419986453.

The spelling of 2820205721 in words is "two billion, eight hundred twenty million, two hundred five thousand, seven hundred twenty-one".