2166904721 has 2 divisors, whose sum is σ = 2166904722. Its totient is φ = 2166904720.

The previous prime is 2166904717. The next prime is 2166904757. The reversal of 2166904721 is 1274096612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1702717696 + 464187025 = 41264^2 + 21545^2 .

It is a cyclic number.

It is not a de Polignac number, because 2166904721 - 2² = 2166904717 is a prime.

It is not a weakly prime, because it can be changed into another prime (2166904781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1083452360 + 1083452361.

It is an arithmetic number, because the mean of its divisors is an integer number (1083452361).

Almost surely, 2^2166904721 is an apocalyptic number.

It is an amenable number.

2166904721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2166904721 is an equidigital number, since it uses as much as digits as its factorization.

2166904721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36288, while the sum is 38.

The square root of 2166904721 is about 46550.0238560626. The cubic root of 2166904721 is about 1294.0367351079.

The spelling of 2166904721 in words is "two billion, one hundred sixty-six million, nine hundred four thousand, seven hundred twenty-one".