21727281 has 8 divisors (see below), whose sum is σ = 29460960. Its totient is φ = 14239232.

The previous prime is 21727271. The next prime is 21727283. The reversal of 21727281 is 18272712.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21727281 - 2⁶ = 21727217 is a prime.

It is a super-2 number, since 2×21727281² = 944149479305922, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21727283) 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, 61200 + ... + 61553.

It is an arithmetic number, because the mean of its divisors is an integer number (3682620).

Almost surely, 2^21727281 is an apocalyptic number.

It is an amenable number.

21727281 is a deficient number, since it is larger than the sum of its proper divisors (7733679).

21727281 is a wasteful number, since it uses less digits than its factorization.

21727281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122815.

The product of its digits is 3136, while the sum is 30.

The square root of 21727281 is about 4661.2531576820. The cubic root of 21727281 is about 279.0412831859.

Adding to 21727281 its reverse (18272712), we get a palindrome (39999993).

It can be divided in two parts, 2172 and 7281, that added together give a triangular number (9453 = T₁₃₇).

The spelling of 21727281 in words is "twenty-one million, seven hundred twenty-seven thousand, two hundred eighty-one".