1997640247 has 4 divisors (see below), whose sum is σ = 1999918936. Its totient is φ = 1995361560.

The previous prime is 1997640241. The next prime is 1997640251. The reversal of 1997640247 is 7420467991.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1997640247 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1997640247.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1997640241) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1138029 + ... + 1139782.

It is an arithmetic number, because the mean of its divisors is an integer number (499979734).

Almost surely, 2^1997640247 is an apocalyptic number.

1997640247 is a deficient number, since it is larger than the sum of its proper divisors (2278689).

1997640247 is an equidigital number, since it uses as much as digits as its factorization.

1997640247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2278688.

The product of its (nonzero) digits is 762048, while the sum is 49.

The square root of 1997640247 is about 44694.9689226875. The cubic root of 1997640247 is about 1259.4253378045.

The spelling of 1997640247 in words is "one billion, nine hundred ninety-seven million, six hundred forty thousand, two hundred forty-seven".