21171613 has 8 divisors (see below), whose sum is σ = 22480632. Its totient is φ = 19869696.

The previous prime is 21171593. The next prime is 21171617. The reversal of 21171613 is 31617112.

It can be written as a sum of positive squares in 4 ways, for example, as 15031129 + 6140484 = 3877^2 + 2478^2 .

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

It is a 6-Lehmer number, since φ(21171613) divides (21171613-1)⁶.

It is a cyclic number.

It is not a de Polignac number, because 21171613 - 2¹⁷ = 21040541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21171617) 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, 5181 + ... + 8317.

It is an arithmetic number, because the mean of its divisors is an integer number (2810079).

Almost surely, 2^21171613 is an apocalyptic number.

It is an amenable number.

21171613 is a deficient number, since it is larger than the sum of its proper divisors (1309019).

21171613 is a wasteful number, since it uses less digits than its factorization.

21171613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3551.

The product of its digits is 252, while the sum is 22.

The square root of 21171613 is about 4601.2621094652. The cubic root of 21171613 is about 276.6419150128.

Adding to 21171613 its reverse (31617112), we get a palindrome (52788725).

It can be divided in two parts, 211 and 71613, that added together give a square (71824 = 268²).

The spelling of 21171613 in words is "twenty-one million, one hundred seventy-one thousand, six hundred thirteen".