21672421 has 2 divisors, whose sum is σ = 21672422. Its totient is φ = 21672420.

The previous prime is 21672403. The next prime is 21672439. The reversal of 21672421 is 12427612.

It is a balanced prime because it is at equal distance from previous prime (21672403) and next prime (21672439).

It can be written as a sum of positive squares in only one way, i.e., 21520321 + 152100 = 4639^2 + 390^2 .

It is a cyclic number.

It is not a de Polignac number, because 21672421 - 2¹¹ = 21670373 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21672401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10836210 + 10836211.

It is an arithmetic number, because the mean of its divisors is an integer number (10836211).

Almost surely, 2^21672421 is an apocalyptic number.

It is an amenable number.

21672421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21672421 is an equidigital number, since it uses as much as digits as its factorization.

21672421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1344, while the sum is 25.

The square root of 21672421 is about 4655.3647547749. The cubic root of 21672421 is about 278.8062314250.

The spelling of 21672421 in words is "twenty-one million, six hundred seventy-two thousand, four hundred twenty-one".