661772791 has 2 divisors, whose sum is σ = 661772792. Its totient is φ = 661772790.

The previous prime is 661772747. The next prime is 661772803. The reversal of 661772791 is 197277166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661772791 - 2¹⁷ = 661641719 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661772711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330886395 + 330886396.

It is an arithmetic number, because the mean of its divisors is an integer number (330886396).

Almost surely, 2^661772791 is an apocalyptic number.

661772791 is a deficient number, since it is larger than the sum of its proper divisors (1).

661772791 is an equidigital number, since it uses as much as digits as its factorization.

661772791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 222264, while the sum is 46.

The square root of 661772791 is about 25724.9449173366. The cubic root of 661772791 is about 871.4376156431.

The spelling of 661772791 in words is "six hundred sixty-one million, seven hundred seventy-two thousand, seven hundred ninety-one".