1981790357 has 2 divisors, whose sum is σ = 1981790358. Its totient is φ = 1981790356.

The previous prime is 1981790243. The next prime is 1981790399. The reversal of 1981790357 is 7530971891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1972603396 + 9186961 = 44414^2 + 3031^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981790357 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981790557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990895178 + 990895179.

It is an arithmetic number, because the mean of its divisors is an integer number (990895179).

Almost surely, 2^1981790357 is an apocalyptic number.

It is an amenable number.

1981790357 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981790357 is an equidigital number, since it uses as much as digits as its factorization.

1981790357 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 476280, while the sum is 50.

The square root of 1981790357 is about 44517.3040176514. The cubic root of 1981790357 is about 1256.0856004532.

The spelling of 1981790357 in words is "one billion, nine hundred eighty-one million, seven hundred ninety thousand, three hundred fifty-seven".