21027761 has 4 divisors (see below), whose sum is σ = 21040500. Its totient is φ = 21015024.

The previous prime is 21027709. The next prime is 21027767. The reversal of 21027761 is 16772012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13432225 + 7595536 = 3665^2 + 2756^2 .

It is a cyclic number.

It is not a de Polignac number, because 21027761 - 2¹⁸ = 20765617 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 21027761.

It is not an unprimeable number, because it can be changed into a prime (21027767) 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, 3446 + ... + 7343.

It is an arithmetic number, because the mean of its divisors is an integer number (5260125).

Almost surely, 2^21027761 is an apocalyptic number.

It is an amenable number.

21027761 is a deficient number, since it is larger than the sum of its proper divisors (12739).

21027761 is a wasteful number, since it uses less digits than its factorization.

21027761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12738.

The product of its (nonzero) digits is 1176, while the sum is 26.

The square root of 21027761 is about 4585.6036680027. The cubic root of 21027761 is about 276.0139363193.

Adding to 21027761 its reverse (16772012), we get a palindrome (37799773).

The spelling of 21027761 in words is "twenty-one million, twenty-seven thousand, seven hundred sixty-one".