21022521 has 8 divisors (see below), whose sum is σ = 30186240. Its totient is φ = 12936912.

The previous prime is 21022517. The next prime is 21022541. The reversal of 21022521 is 12522012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21022521 - 2² = 21022517 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21022521.

It is not an unprimeable number, because it can be changed into a prime (21022541) 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 7 ways as a sum of consecutive naturals, for example, 269481 + ... + 269558.

It is an arithmetic number, because the mean of its divisors is an integer number (3773280).

Almost surely, 2^21022521 is an apocalyptic number.

It is an amenable number.

21022521 is a deficient number, since it is larger than the sum of its proper divisors (9163719).

21022521 is a wasteful number, since it uses less digits than its factorization.

21022521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 539055.

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21022521 is about 4585.0322790576. The cubic root of 21022521 is about 275.9910073735.

Adding to 21022521 its reverse (12522012), we get a palindrome (33544533).

The spelling of 21022521 in words is "twenty-one million, twenty-two thousand, five hundred twenty-one".