1997857109 has 2 divisors, whose sum is σ = 1997857110. Its totient is φ = 1997857108.

The previous prime is 1997857079. The next prime is 1997857123. The reversal of 1997857109 is 9017587991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1249834609 + 748022500 = 35353^2 + 27350^2 .

It is a cyclic number.

It is not a de Polignac number, because 1997857109 - 2¹⁶ = 1997791573 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1997857129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 998928554 + 998928555.

It is an arithmetic number, because the mean of its divisors is an integer number (998928555).

Almost surely, 2^1997857109 is an apocalyptic number.

It is an amenable number.

1997857109 is a deficient number, since it is larger than the sum of its proper divisors (1).

1997857109 is an equidigital number, since it uses as much as digits as its factorization.

1997857109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1428840, while the sum is 56.

The square root of 1997857109 is about 44697.3948793439. The cubic root of 1997857109 is about 1259.4709101768.

The spelling of 1997857109 in words is "one billion, nine hundred ninety-seven million, eight hundred fifty-seven thousand, one hundred nine".