21542213 has 24 divisors (see below), whose sum is σ = 28957824. Its totient is φ = 15792000.

The previous prime is 21542173. The next prime is 21542231. The reversal of 21542213 is 31224512.

It is not a de Polignac number, because 21542213 - 2¹² = 21538117 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7988 + ... + 10338.

It is an arithmetic number, because the mean of its divisors is an integer number (1206576).

Almost surely, 2^21542213 is an apocalyptic number.

It is an amenable number.

21542213 is a deficient number, since it is larger than the sum of its proper divisors (7415611).

21542213 is a wasteful number, since it uses less digits than its factorization.

21542213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2393 (or 2386 counting only the distinct ones).

The product of its digits is 480, while the sum is 20.

The square root of 21542213 is about 4641.3589604770. The cubic root of 21542213 is about 278.2467531232.

Adding to 21542213 its reverse (31224512), we get a palindrome (52766725).

The spelling of 21542213 in words is "twenty-one million, five hundred forty-two thousand, two hundred thirteen".