1901981 has 2 divisors, whose sum is σ = 1901982. Its totient is φ = 1901980.

The previous prime is 1901969. The next prime is 1901987. The reversal of 1901981 is 1891091.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1136356 + 765625 = 1066^2 + 875^2 .

It is a cyclic number.

It is not a de Polignac number, because 1901981 - 2⁶ = 1901917 is a prime.

It is a super-2 number, since 2×1901981² = 7235063448722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1901987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 950990 + 950991.

It is an arithmetic number, because the mean of its divisors is an integer number (950991).

2^1901981 is an apocalyptic number.

It is an amenable number.

1901981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1901981 is an equidigital number, since it uses as much as digits as its factorization.

1901981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 29.

The square root of 1901981 is about 1379.1232722277. The cubic root of 1901981 is about 123.8992634847.

It can be divided in two parts, 1901 and 981, that added together give a palindrome (2882).

The spelling of 1901981 in words is "one million, nine hundred one thousand, nine hundred eighty-one".