10218985921 has 3 divisors (see below), whose sum is σ = 10219087011.
Its totient is φ = 10218884832.
The previous prime is 10218985913. The next prime is 10218985939. The reversal of 10218985921 is 12958981201.
It is a happy number.
The square root of 10218985921 is 101089.
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, and also an emirpimes, since its reverse is a distinct semiprime: 12958981201 = 2909 ⋅4454789.
It can be written as a sum of positive squares in only one way, i.e., 1163560321 + 9055425600 = 34111^2 + 95160^2
It is not a de Polignac number, because 10218985921 - 23 = 10218985913 is a prime.
It is a Duffinian number.
It is not an unprimeable number, because it can be changed into a prime (10218985901) 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, 50545 + ... + 151633.
It is an arithmetic number, because the mean of its divisors is an integer number (3406362337).
Almost surely, 210218985921 is an apocalyptic number.
10218985921 is the 101089-th square number.
10218985921 is the 50545-th centered octagonal number.
It is an amenable number.
10218985921 is a deficient number, since it is larger than the sum of its proper divisors (101090).
10218985921 is an frugal number, since it uses more digits than its factorization.
10218985921 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 202178 (or 101089 counting only the distinct ones).
The product of its (nonzero) digits is 103680, while the sum is 46.
The spelling of 10218985921 in words is "ten billion, two hundred eighteen million, nine hundred eighty-five thousand, nine hundred twenty-one".