21868198641 has 21 divisors (see below), whose sum is σ = 32793286651. Its totient is φ = 14576137272.

The previous prime is 21868198609. The next prime is 21868198657. The reversal of 21868198641 is 14689186812.

It is a happy number.

The square root of 21868198641 is 147879.

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

It can be written as a sum of positive squares in only one way, i.e., 21852230625 + 15968016 = 147825^2 + 3996^2 .

It is not a de Polignac number, because 21868198641 - 2⁵ = 21868198609 is a prime.

It is a super-2 number, since 2×21868198641² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21868198691) 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 20 ways as a sum of consecutive naturals, for example, 3989995 + ... + 3995471.

Almost surely, 2^21868198641 is an apocalyptic number.

21868198641 is the 147879-th square number.

21868198641 is the 73940-th centered octagonal number.

It is an amenable number.

21868198641 is a deficient number, since it is larger than the sum of its proper divisors (10925088010).

21868198641 is an frugal number, since it uses more digits than its factorization.

21868198641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10972 (or 5480 counting only the distinct ones).

The product of its digits is 1327104, while the sum is 54.

The spelling of 21868198641 in words is "twenty-one billion, eight hundred sixty-eight million, one hundred ninety-eight thousand, six hundred forty-one".