1899721 has 2 divisors, whose sum is σ = 1899722. Its totient is φ = 1899720.

The previous prime is 1899707. The next prime is 1899757. The reversal of 1899721 is 1279981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 978121 + 921600 = 989^2 + 960^2 .

It is a cyclic number.

It is not a de Polignac number, because 1899721 - 2¹³ = 1891529 is a prime.

It is not a weakly prime, because it can be changed into another prime (1899701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 949860 + 949861.

It is an arithmetic number, because the mean of its divisors is an integer number (949861).

2^1899721 is an apocalyptic number.

It is an amenable number.

1899721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1899721 is an equidigital number, since it uses as much as digits as its factorization.

1899721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 37.

The square root of 1899721 is about 1378.3036675566. The cubic root of 1899721 is about 123.8501702296.

The spelling of 1899721 in words is "one million, eight hundred ninety-nine thousand, seven hundred twenty-one".