1681557969001 has 3 divisors (see below), whose sum is σ = 1681559265751. Its totient is φ = 1681556672252.

The previous prime is 1681557968971. The next prime is 1681557969029. The reversal of 1681557969001 is 1009697551861.

The square root of 1681557969001 is 1296749.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 1091396000601 + 590161968400 = 1044699^2 + 768220^2 .

It is not a de Polignac number, because 1681557969001 - 2⁷ = 1681557968873 is a prime.

It is a super-2 number, since 2×1681557969001² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1681557969031) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 648375 + ... + 1945123.

Almost surely, 2^{1681557969001} is an apocalyptic number.

1681557969001 is the 1296749-th square number.

1681557969001 is the 648375-th centered octagonal number.

It is an amenable number.

1681557969001 is a deficient number, since it is larger than the sum of its proper divisors (1296750).

1681557969001 is an frugal number, since it uses more digits than its factorization.

1681557969001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2593498 (or 1296749 counting only the distinct ones).

The product of its (nonzero) digits is 4082400, while the sum is 58.

The spelling of 1681557969001 in words is "one trillion, six hundred eighty-one billion, five hundred fifty-seven million, nine hundred sixty-nine thousand, one".