1997721243 has 12 divisors (see below), whose sum is σ = 3297825648. Its totient is φ = 1141554960.

The previous prime is 1997721217. The next prime is 1997721283. The reversal of 1997721243 is 3421277991.

It is not a de Polignac number, because 1997721243 - 2⁹ = 1997720731 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (1997721283) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15854868 + ... + 15854993.

It is an arithmetic number, because the mean of its divisors is an integer number (274818804).

Almost surely, 2^1997721243 is an apocalyptic number.

1997721243 is a deficient number, since it is larger than the sum of its proper divisors (1300104405).

1997721243 is a wasteful number, since it uses less digits than its factorization.

1997721243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31709874 (or 31709871 counting only the distinct ones).

The product of its digits is 190512, while the sum is 45.

The square root of 1997721243 is about 44695.8750110119. The cubic root of 1997721243 is about 1259.4423590602.

The spelling of 1997721243 in words is "one billion, nine hundred ninety-seven million, seven hundred twenty-one thousand, two hundred forty-three".