661947397 has 2 divisors, whose sum is σ = 661947398. Its totient is φ = 661947396.

The previous prime is 661947361. The next prime is 661947439. The reversal of 661947397 is 793749166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 333939076 + 328008321 = 18274^2 + 18111^2 .

It is a cyclic number.

It is not a de Polignac number, because 661947397 - 2¹⁵ = 661914629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661947317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330973698 + 330973699.

It is an arithmetic number, because the mean of its divisors is an integer number (330973699).

Almost surely, 2^661947397 is an apocalyptic number.

It is an amenable number.

661947397 is a deficient number, since it is larger than the sum of its proper divisors (1).

661947397 is an equidigital number, since it uses as much as digits as its factorization.

661947397 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1714608, while the sum is 52.

The square root of 661947397 is about 25728.3384034026. The cubic root of 661947397 is about 871.5142506343.

The spelling of 661947397 in words is "six hundred sixty-one million, nine hundred forty-seven thousand, three hundred ninety-seven".