21021421 has 4 divisors (see below), whose sum is σ = 21187072. Its totient is φ = 20855772.

The previous prime is 21021419. The next prime is 21021431. The reversal of 21021421 is 12412012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21021421 - 2¹ = 21021419 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 (21021431) 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 3 ways as a sum of consecutive naturals, for example, 82635 + ... + 82888.

It is an arithmetic number, because the mean of its divisors is an integer number (5296768).

Almost surely, 2^21021421 is an apocalyptic number.

It is an amenable number.

21021421 is a deficient number, since it is larger than the sum of its proper divisors (165651).

21021421 is a wasteful number, since it uses less digits than its factorization.

21021421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165650.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21021421 is about 4584.9123219534. The cubic root of 21021421 is about 275.9861935613.

Adding to 21021421 its reverse (12412012), we get a palindrome (33433433).

The spelling of 21021421 in words is "twenty-one million, twenty-one thousand, four hundred twenty-one".