100821681 has 9 divisors (see below), whose sum is σ = 145674841. Its totient is φ = 67194372.

The previous prime is 100821671. The next prime is 100821683. The reversal of 100821681 is 186128001.

The square root of 100821681 is 10041.

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

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 100821681 - 2²³ = 92433073 is a prime.

It is a super-2 number, since 2×100821681² = 20330022719331522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (100821683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 28450 + ... + 31796.

Almost surely, 2^100821681 is an apocalyptic number.

100821681 is the 10041-st square number.

100821681 is the 5021-st centered octagonal number.

It is an amenable number.

100821681 is a deficient number, since it is larger than the sum of its proper divisors (44853160).

100821681 is an frugal number, since it uses more digits than its factorization.

100821681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6700 (or 3350 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The cubic root of 100821681 is about 465.4267189395.

Adding to 100821681 its reverse (186128001), we get a palindrome (286949682).

The spelling of 100821681 in words is "one hundred million, eight hundred twenty-one thousand, six hundred eighty-one".