21521411 has 4 divisors (see below), whose sum is σ = 21666000. Its totient is φ = 21376824.

The previous prime is 21521389. The next prime is 21521413. The reversal of 21521411 is 11412512.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21521411 is a prime.

It is a super-2 number, since 2×21521411² = 926342262861842, which contains 22 as substring.

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 21521411.

It is not an unprimeable number, because it can be changed into a prime (21521413) 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, 72071 + ... + 72368.

It is an arithmetic number, because the mean of its divisors is an integer number (5416500).

Almost surely, 2^21521411 is an apocalyptic number.

21521411 is a deficient number, since it is larger than the sum of its proper divisors (144589).

21521411 is a wasteful number, since it uses less digits than its factorization.

21521411 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144588.

The product of its digits is 80, while the sum is 17.

The square root of 21521411 is about 4639.1174807284. The cubic root of 21521411 is about 278.1571623118.

Adding to 21521411 its reverse (11412512), we get a palindrome (32933923).

The spelling of 21521411 in words is "twenty-one million, five hundred twenty-one thousand, four hundred eleven".