661021211 has 2 divisors, whose sum is σ = 661021212. Its totient is φ = 661021210.

The previous prime is 661021199. The next prime is 661021223. The reversal of 661021211 is 112120166.

661021211 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a balanced prime because it is at equal distance from previous prime (661021199) and next prime (661021223).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661021211 is a prime.

It is not a weakly prime, because it can be changed into another prime (661021111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330510605 + 330510606.

It is an arithmetic number, because the mean of its divisors is an integer number (330510606).

Almost surely, 2^661021211 is an apocalyptic number.

661021211 is a deficient number, since it is larger than the sum of its proper divisors (1).

661021211 is an equidigital number, since it uses as much as digits as its factorization.

661021211 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 661021211 is about 25710.3327671969. The cubic root of 661021211 is about 871.1075914040.

Adding to 661021211 its reverse (112120166), we get a palindrome (773141377).

The spelling of 661021211 in words is "six hundred sixty-one million, twenty-one thousand, two hundred eleven".