21677221 has 2 divisors, whose sum is σ = 21677222. Its totient is φ = 21677220.

The previous prime is 21677213. The next prime is 21677231. The reversal of 21677221 is 12277612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18576100 + 3101121 = 4310^2 + 1761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21677221 - 2³ = 21677213 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21677221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21677231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10838610 + 10838611.

It is an arithmetic number, because the mean of its divisors is an integer number (10838611).

Almost surely, 2^21677221 is an apocalyptic number.

It is an amenable number.

21677221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21677221 is an equidigital number, since it uses as much as digits as its factorization.

21677221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2352, while the sum is 28.

The square root of 21677221 is about 4655.8802604878. The cubic root of 21677221 is about 278.8268132068.

The spelling of 21677221 in words is "twenty-one million, six hundred seventy-seven thousand, two hundred twenty-one".