21608361 has 6 divisors (see below), whose sum is σ = 31212090. Its totient is φ = 14405568.

The previous prime is 21608359. The next prime is 21608369. The reversal of 21608361 is 16380612.

21608361 is a `hidden beast` number, since 21 + 608 + 36 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 15848361 + 5760000 = 3981^2 + 2400^2 .

It is not a de Polignac number, because 21608361 - 2¹ = 21608359 is a prime.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21608369) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1200456 + ... + 1200473.

It is an arithmetic number, because the mean of its divisors is an integer number (5202015).

Almost surely, 2^21608361 is an apocalyptic number.

It is an amenable number.

21608361 is a deficient number, since it is larger than the sum of its proper divisors (9603729).

21608361 is a wasteful number, since it uses less digits than its factorization.

21608361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2400935 (or 2400932 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21608361 is about 4648.4794288025. The cubic root of 21608361 is about 278.5312590149.

Adding to 21608361 its reverse (16380612), we get a palindrome (37988973).

The spelling of 21608361 in words is "twenty-one million, six hundred eight thousand, three hundred sixty-one".