21613201 has 3 divisors (see below), whose sum is σ = 21617851. Its totient is φ = 21608552.

The previous prime is 21613199. The next prime is 21613213. The reversal of 21613201 is 10231612.

The square root of 21613201 is 4649.

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.

It can be written as a sum of positive squares in only one way, i.e., 21150801 + 462400 = 4599^2 + 680^2 .

It is not a de Polignac number, because 21613201 - 2¹ = 21613199 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21616201) 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 2 ways as a sum of consecutive naturals, for example, 2325 + ... + 6973.

Almost surely, 2^21613201 is an apocalyptic number.

21613201 is the 4649-th square number.

21613201 is the 2325-th centered octagonal number.

It is an amenable number.

21613201 is a deficient number, since it is larger than the sum of its proper divisors (4650).

21613201 is an frugal number, since it uses more digits than its factorization.

21613201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9298 (or 4649 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 16.

The cubic root of 21613201 is about 278.5520532907.

Multiplying 21613201 by its sum of digits (16), we get a square (345811216 = 18596²).

Adding to 21613201 its reverse (10231612), we get a palindrome (31844813).

The spelling of 21613201 in words is "twenty-one million, six hundred thirteen thousand, two hundred one".