661797221 has 2 divisors, whose sum is σ = 661797222. Its totient is φ = 661797220.

The previous prime is 661797211. The next prime is 661797229. The reversal of 661797221 is 122797166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 377874721 + 283922500 = 19439^2 + 16850^2 .

It is a cyclic number.

It is not a de Polignac number, because 661797221 - 2¹⁰ = 661796197 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661797229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330898610 + 330898611.

It is an arithmetic number, because the mean of its divisors is an integer number (330898611).

Almost surely, 2^661797221 is an apocalyptic number.

It is an amenable number.

661797221 is a deficient number, since it is larger than the sum of its proper divisors (1).

661797221 is an equidigital number, since it uses as much as digits as its factorization.

661797221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 63504, while the sum is 41.

The square root of 661797221 is about 25725.4197439031. The cubic root of 661797221 is about 871.4483388395.

The spelling of 661797221 in words is "six hundred sixty-one million, seven hundred ninety-seven thousand, two hundred twenty-one".