21261317 has 16 divisors (see below), whose sum is σ = 26611200. Its totient is φ = 16502640.

The previous prime is 21261293. The next prime is 21261337. The reversal of 21261317 is 71316212.

It is not a de Polignac number, because 21261317 - 2¹⁰ = 21260293 is a prime.

It is a super-4 number, since 4×21261317⁴ (a number of 30 digits) contains 4444 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21261292 and 21261301.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21261337) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31934 + ... + 32592.

It is an arithmetic number, because the mean of its divisors is an integer number (1663200).

Almost surely, 2^21261317 is an apocalyptic number.

It is an amenable number.

21261317 is a deficient number, since it is larger than the sum of its proper divisors (5349883).

21261317 is a wasteful number, since it uses less digits than its factorization.

21261317 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1096.

The product of its digits is 504, while the sum is 23.

The square root of 21261317 is about 4610.9995662546. Note that the first 3 decimals coincide. The cubic root of 21261317 is about 277.0320745527.

Adding to 21261317 its reverse (71316212), we get a palindrome (92577529).

It can be divided in two parts, 2126 and 1317, that added together give a palindrome (3443).

The spelling of 21261317 in words is "twenty-one million, two hundred sixty-one thousand, three hundred seventeen".