21117261 has 16 divisors (see below), whose sum is σ = 31177728. Its totient is φ = 12606000.

The previous prime is 21117259. The next prime is 21117263. The reversal of 21117261 is 16271112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21117259) and next prime (21117263).

It is not a de Polignac number, because 21117261 - 2¹ = 21117259 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21117263) 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 15 ways as a sum of consecutive naturals, for example, 2565 + ... + 6986.

It is an arithmetic number, because the mean of its divisors is an integer number (1948608).

Almost surely, 2^21117261 is an apocalyptic number.

It is an amenable number.

21117261 is a deficient number, since it is larger than the sum of its proper divisors (10060467).

21117261 is a wasteful number, since it uses less digits than its factorization.

21117261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9632.

The product of its digits is 168, while the sum is 21.

The square root of 21117261 is about 4595.3521083808. The cubic root of 21117261 is about 276.4049794104.

Adding to 21117261 its reverse (16271112), we get a palindrome (37388373).

The spelling of 21117261 in words is "twenty-one million, one hundred seventeen thousand, two hundred sixty-one".