661244261 has 2 divisors, whose sum is σ = 661244262. Its totient is φ = 661244260.

The previous prime is 661244237. The next prime is 661244321. The reversal of 661244261 is 162442166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 387341761 + 273902500 = 19681^2 + 16550^2 .

It is a cyclic number.

It is not a de Polignac number, because 661244261 - 2⁶ = 661244197 is a prime.

It is a super-2 number, since 2×661244261² = 874487945410872242, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661244201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330622130 + 330622131.

It is an arithmetic number, because the mean of its divisors is an integer number (330622131).

Almost surely, 2^661244261 is an apocalyptic number.

It is an amenable number.

661244261 is a deficient number, since it is larger than the sum of its proper divisors (1).

661244261 is an equidigital number, since it uses as much as digits as its factorization.

661244261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 32.

The square root of 661244261 is about 25714.6701514913. The cubic root of 661244261 is about 871.2055603721.

The spelling of 661244261 in words is "six hundred sixty-one million, two hundred forty-four thousand, two hundred sixty-one".