21527321 has 6 divisors (see below), whose sum is σ = 22868430. Its totient is φ = 20260736.

The previous prime is 21527249. The next prime is 21527329. The reversal of 21527321 is 12372512.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 10471696 + 11055625 = 3236^2 + 3325^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21527321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21527329) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36956 + ... + 37533.

It is an arithmetic number, because the mean of its divisors is an integer number (3811405).

Almost surely, 2^21527321 is an apocalyptic number.

It is an amenable number.

21527321 is a deficient number, since it is larger than the sum of its proper divisors (1341109).

21527321 is an equidigital number, since it uses as much as digits as its factorization.

21527321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74523 (or 74506 counting only the distinct ones).

The product of its digits is 840, while the sum is 23.

The square root of 21527321 is about 4639.7544116041. The cubic root of 21527321 is about 278.1826215839.

Adding to 21527321 its reverse (12372512), we get a palindrome (33899833).

The spelling of 21527321 in words is "twenty-one million, five hundred twenty-seven thousand, three hundred twenty-one".