21617261 has 8 divisors (see below), whose sum is σ = 22834944. Its totient is φ = 20432160.

The previous prime is 21617249. The next prime is 21617273. The reversal of 21617261 is 16271612.

It is an interprime number because it is at equal distance from previous prime (21617249) and next prime (21617273).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21617261 - 2¹⁰ = 21616237 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21617261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21617201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6776 + ... + 9441.

It is an arithmetic number, because the mean of its divisors is an integer number (2854368).

Almost surely, 2^21617261 is an apocalyptic number.

It is an amenable number.

21617261 is a deficient number, since it is larger than the sum of its proper divisors (1217683).

21617261 is a wasteful number, since it uses less digits than its factorization.

21617261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16291.

The product of its digits is 1008, while the sum is 26.

The square root of 21617261 is about 4649.4366325395. The cubic root of 21617261 is about 278.5694940287.

Adding to 21617261 its reverse (16271612), we get a palindrome (37888873).

The spelling of 21617261 in words is "twenty-one million, six hundred seventeen thousand, two hundred sixty-one".