21571421 has 2 divisors, whose sum is σ = 21571422. Its totient is φ = 21571420.

The previous prime is 21571397. The next prime is 21571439. The reversal of 21571421 is 12417512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19483396 + 2088025 = 4414^2 + 1445^2 .

It is a cyclic number.

It is not a de Polignac number, because 21571421 - 2⁶ = 21571357 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21571471) 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, 10785710 + 10785711.

It is an arithmetic number, because the mean of its divisors is an integer number (10785711).

Almost surely, 2^21571421 is an apocalyptic number.

It is an amenable number.

21571421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21571421 is an equidigital number, since it uses as much as digits as its factorization.

21571421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 560, while the sum is 23.

The square root of 21571421 is about 4644.5043869072. The cubic root of 21571421 is about 278.3724499109.

Adding to 21571421 its reverse (12417512), we get a palindrome (33988933).

The spelling of 21571421 in words is "twenty-one million, five hundred seventy-one thousand, four hundred twenty-one".