21541487 has 4 divisors (see below), whose sum is σ = 23499816. Its totient is φ = 19583160.

The previous prime is 21541477. The next prime is 21541493. The reversal of 21541487 is 78414512.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21541487 - 2⁶ = 21541423 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21541417) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 979148 + ... + 979169.

It is an arithmetic number, because the mean of its divisors is an integer number (5874954).

Almost surely, 2^21541487 is an apocalyptic number.

21541487 is a deficient number, since it is larger than the sum of its proper divisors (1958329).

21541487 is a wasteful number, since it uses less digits than its factorization.

21541487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1958328.

The product of its digits is 8960, while the sum is 32.

The square root of 21541487 is about 4641.2807499655. The cubic root of 21541487 is about 278.2436273315.

Adding to 21541487 its reverse (78414512), we get a palindrome (99955999).

The spelling of 21541487 in words is "twenty-one million, five hundred forty-one thousand, four hundred eighty-seven".