21231421 has 2 divisors, whose sum is σ = 21231422. Its totient is φ = 21231420.

The previous prime is 21231407. The next prime is 21231433. The reversal of 21231421 is 12413212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19096900 + 2134521 = 4370^2 + 1461^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231421 - 2⁵ = 21231389 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21231395 and 21231404.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201421) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615710 + 10615711.

It is an arithmetic number, because the mean of its divisors is an integer number (10615711).

Almost surely, 2^21231421 is an apocalyptic number.

It is an amenable number.

21231421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231421 is an equidigital number, since it uses as much as digits as its factorization.

21231421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96, while the sum is 16.

The square root of 21231421 is about 4607.7566124959. The cubic root of 21231421 is about 276.9021667042.

Adding to 21231421 its reverse (12413212), we get a palindrome (33644633).

The spelling of 21231421 in words is "twenty-one million, two hundred thirty-one thousand, four hundred twenty-one".