21521541 has 24 divisors (see below), whose sum is σ = 30906304. Its totient is φ = 13317120.

The previous prime is 21521527. The next prime is 21521557. The reversal of 21521541 is 14512512.

21521541 is nontrivially palindromic in base 4.

It is not a de Polignac number, because 21521541 - 2⁷ = 21521413 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521041) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 89181 + ... + 89421.

Almost surely, 2^21521541 is an apocalyptic number.

It is an amenable number.

21521541 is a deficient number, since it is larger than the sum of its proper divisors (9384763).

21521541 is a wasteful number, since it uses less digits than its factorization.

21521541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 381 (or 364 counting only the distinct ones).

The product of its digits is 400, while the sum is 21.

The square root of 21521541 is about 4639.1314919929. The cubic root of 21521541 is about 278.1577223798.

The spelling of 21521541 in words is "twenty-one million, five hundred twenty-one thousand, five hundred forty-one".