21644000161 has 9 divisors (see below), whose sum is σ = 25178912499. Its totient is φ = 18551117424.

The previous prime is 21644000117. The next prime is 21644000197. The reversal of 21644000161 is 16100044612.

The square root of 21644000161 is 147119.

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., 18533025 + 21625467136 = 4305^2 + 147056^2 .

It is not a de Polignac number, because 21644000161 - 2²¹ = 21641903009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21644009161) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1019325 + ... + 1040341.

Almost surely, 2^21644000161 is an apocalyptic number.

21644000161 is the 147119-th square number.

21644000161 is the 73560-th centered octagonal number.

It is an amenable number.

21644000161 is a deficient number, since it is larger than the sum of its proper divisors (3534912338).

21644000161 is an frugal number, since it uses more digits than its factorization.

21644000161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42048 (or 21024 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

Multiplying 21644000161 by its sum of digits (25), we get a square (541100004025 = 735595²).

Adding to 21644000161 its reverse (16100044612), we get a palindrome (37744044773).

The spelling of 21644000161 in words is "twenty-one billion, six hundred forty-four million, one hundred sixty-one", and thus it is an aban number.