21117761 has 4 divisors (see below), whose sum is σ = 24134592. Its totient is φ = 18100932.

The previous prime is 21117751. The next prime is 21117763. The reversal of 21117761 is 16771112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21117761 - 2⁶ = 21117697 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 21117761.

It is not an unprimeable number, because it can be changed into a prime (21117763) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1508405 + ... + 1508418.

It is an arithmetic number, because the mean of its divisors is an integer number (6033648).

Almost surely, 2^21117761 is an apocalyptic number.

It is an amenable number.

21117761 is a deficient number, since it is larger than the sum of its proper divisors (3016831).

21117761 is an equidigital number, since it uses as much as digits as its factorization.

21117761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3016830.

The product of its digits is 588, while the sum is 26.

The square root of 21117761 is about 4595.4065108541. The cubic root of 21117761 is about 276.4071609022.

Adding to 21117761 its reverse (16771112), we get a palindrome (37888873).

The spelling of 21117761 in words is "twenty-one million, one hundred seventeen thousand, seven hundred sixty-one".