1919291981 has 2 divisors, whose sum is σ = 1919291982. Its totient is φ = 1919291980.

The previous prime is 1919291977. The next prime is 1919291987. The reversal of 1919291981 is 1891929191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1142778025 + 776513956 = 33805^2 + 27866^2 .

It is a cyclic number.

It is not a de Polignac number, because 1919291981 - 2² = 1919291977 is a prime.

It is a super-2 number, since 2×1919291981² = 7367363416661808722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1919291987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 959645990 + 959645991.

It is an arithmetic number, because the mean of its divisors is an integer number (959645991).

Almost surely, 2^1919291981 is an apocalyptic number.

It is an amenable number.

1919291981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1919291981 is an equidigital number, since it uses as much as digits as its factorization.

1919291981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 104976, while the sum is 50.

The square root of 1919291981 is about 43809.7247309316. The cubic root of 1919291981 is about 1242.7402072337.

The spelling of 1919291981 in words is "one billion, nine hundred nineteen million, two hundred ninety-one thousand, nine hundred eighty-one".