21546221 has 2 divisors, whose sum is σ = 21546222. Its totient is φ = 21546220.

The previous prime is 21546211. The next prime is 21546227. The reversal of 21546221 is 12264512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14523721 + 7022500 = 3811^2 + 2650^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21546221 is a prime.

It is a Chen prime.

It is equal to p_1362308 and since 21546221 and 1362308 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21546227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10773110 + 10773111.

It is an arithmetic number, because the mean of its divisors is an integer number (10773111).

Almost surely, 2^21546221 is an apocalyptic number.

It is an amenable number.

21546221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21546221 is an equidigital number, since it uses as much as digits as its factorization.

21546221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 23.

The square root of 21546221 is about 4641.7907104909. The cubic root of 21546221 is about 278.2640082962.

The spelling of 21546221 in words is "twenty-one million, five hundred forty-six thousand, two hundred twenty-one".