101817789921 has 9 divisors (see below), whose sum is σ = 147071523729. Its totient is φ = 67877888436.

The previous prime is 101817789901. The next prime is 101817789923. The reversal of 101817789921 is 129987718101.

The square root of 101817789921 is 319089.

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 101817789921 - 2¹³ = 101817781729 is a prime.

It is not an unprimeable number, because it can be changed into a prime (101817789923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 904086 + ... + 1010448.

Almost surely, 2^101817789921 is an apocalyptic number.

101817789921 is the 319089-th square number.

101817789921 is the 159545-th centered octagonal number.

It is an amenable number.

101817789921 is a deficient number, since it is larger than the sum of its proper divisors (45253733808).

101817789921 is an frugal number, since it uses more digits than its factorization.

101817789921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212732 (or 106366 counting only the distinct ones).

The product of its (nonzero) digits is 508032, while the sum is 54.

The spelling of 101817789921 in words is "one hundred one billion, eight hundred seventeen million, seven hundred eighty-nine thousand, nine hundred twenty-one".