21121421 has 4 divisors (see below), whose sum is σ = 21131292. Its totient is φ = 21111552.

The previous prime is 21121417. The next prime is 21121453. The reversal of 21121421 is 12412112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 21058921 + 62500 = 4589^2 + 250^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121421 - 2² = 21121417 is a prime.

It is a super-2 number, since 2×21121421² = 892228850118482, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21121396 and 21121405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121411) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 230 + ... + 6503.

It is an arithmetic number, because the mean of its divisors is an integer number (5282823).

Almost surely, 2^21121421 is an apocalyptic number.

It is an amenable number.

21121421 is a deficient number, since it is larger than the sum of its proper divisors (9871).

21121421 is an equidigital number, since it uses as much as digits as its factorization.

21121421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9870.

The product of its digits is 32, while the sum is 14.

The square root of 21121421 is about 4595.8047173482. The cubic root of 21121421 is about 276.4231283742.

Adding to 21121421 its reverse (12412112), we get a palindrome (33533533).

The spelling of 21121421 in words is "twenty-one million, one hundred twenty-one thousand, four hundred twenty-one".