1997385797521 has 9 divisors (see below), whose sum is σ = 2052881952849. Its totient is φ = 1943351519184.

The previous prime is 1997385797479. The next prime is 1997385797531. The reversal of 1997385797521 is 1257975837991.

The square root of 1997385797521 is 1413289.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 168724599121 + 1828661198400 = 410761^2 + 1352280^2 .

It is not a de Polignac number, because 1997385797521 - 2²⁹ = 1996848926609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1997385797531) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 52272595 + ... + 52310791.

It is an arithmetic number, because the mean of its divisors is an integer number (228097994761).

Almost surely, 2^{1997385797521} is an apocalyptic number.

1997385797521 is the 1413289-th square number.

1997385797521 is the 706645-th centered octagonal number.

It is an amenable number.

1997385797521 is a deficient number, since it is larger than the sum of its proper divisors (55496155328).

1997385797521 is an frugal number, since it uses more digits than its factorization.

1997385797521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76468 (or 38234 counting only the distinct ones).

The product of its digits is 300056400, while the sum is 73.

The spelling of 1997385797521 in words is "one trillion, nine hundred ninety-seven billion, three hundred eighty-five million, seven hundred ninety-seven thousand, five hundred twenty-one".