1889866721 has 2 divisors, whose sum is σ = 1889866722. Its totient is φ = 1889866720.

The previous prime is 1889866661. The next prime is 1889866747. The reversal of 1889866721 is 1276689881.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1783879696 + 105987025 = 42236^2 + 10295^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1889866721 is a prime.

It is not a weakly prime, because it can be changed into another prime (1889866621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 944933360 + 944933361.

It is an arithmetic number, because the mean of its divisors is an integer number (944933361).

Almost surely, 2^1889866721 is an apocalyptic number.

It is an amenable number.

1889866721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1889866721 is an equidigital number, since it uses as much as digits as its factorization.

1889866721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2322432, while the sum is 56.

The square root of 1889866721 is about 43472.5973574159. The cubic root of 1889866721 is about 1236.3565267841.

The spelling of 1889866721 in words is "one billion, eight hundred eighty-nine million, eight hundred sixty-six thousand, seven hundred twenty-one".