211551421 has 2 divisors, whose sum is σ = 211551422. Its totient is φ = 211551420.

The previous prime is 211551419. The next prime is 211551437. The reversal of 211551421 is 124155112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202635225 + 8916196 = 14235^2 + 2986^2 .

It is a cyclic number.

It is not a de Polignac number, because 211551421 - 2¹ = 211551419 is a prime.

Together with 211551419, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 211551392 and 211551401.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (211551121) 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, 105775710 + 105775711.

It is an arithmetic number, because the mean of its divisors is an integer number (105775711).

Almost surely, 2^211551421 is an apocalyptic number.

It is an amenable number.

211551421 is a deficient number, since it is larger than the sum of its proper divisors (1).

211551421 is an equidigital number, since it uses as much as digits as its factorization.

211551421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 400, while the sum is 22.

The square root of 211551421 is about 14544.8073552041. The cubic root of 211551421 is about 595.8523396266.

The spelling of 211551421 in words is "two hundred eleven million, five hundred fifty-one thousand, four hundred twenty-one".