21122421 has 16 divisors (see below), whose sum is σ = 29211840. Its totient is φ = 13566080.

The previous prime is 21122419. The next prime is 21122443. The reversal of 21122421 is 12422112.

It is not a de Polignac number, because 21122421 - 2¹ = 21122419 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21122421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122221) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9175 + ... + 11243.

It is an arithmetic number, because the mean of its divisors is an integer number (1825740).

Almost surely, 2^21122421 is an apocalyptic number.

It is an amenable number.

21122421 is a deficient number, since it is larger than the sum of its proper divisors (8089419).

21122421 is a wasteful number, since it uses less digits than its factorization.

21122421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2196.

The product of its digits is 64, while the sum is 15.

The square root of 21122421 is about 4595.9135109356. The cubic root of 21122421 is about 276.4274907506.

Adding to 21122421 its reverse (12422112), we get a palindrome (33544533).

The spelling of 21122421 in words is "twenty-one million, one hundred twenty-two thousand, four hundred twenty-one".