21542371 has 4 divisors (see below), whose sum is σ = 22676200. Its totient is φ = 20408544.

The previous prime is 21542363. The next prime is 21542377. The reversal of 21542371 is 17324512.

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 21542371 - 2³ = 21542363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21542377) 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, 566886 + ... + 566923.

It is an arithmetic number, because the mean of its divisors is an integer number (5669050).

Almost surely, 2^21542371 is an apocalyptic number.

21542371 is a deficient number, since it is larger than the sum of its proper divisors (1133829).

21542371 is a wasteful number, since it uses less digits than its factorization.

21542371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1133828.

The product of its digits is 1680, while the sum is 25.

The square root of 21542371 is about 4641.3759813228. The cubic root of 21542371 is about 278.2474333827.

Adding to 21542371 its reverse (17324512), we get a palindrome (38866883).

The spelling of 21542371 in words is "twenty-one million, five hundred forty-two thousand, three hundred seventy-one".