661904869 has 2 divisors, whose sum is σ = 661904870. Its totient is φ = 661904868.

The previous prime is 661904857. The next prime is 661904917. The reversal of 661904869 is 968409166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 572979969 + 88924900 = 23937^2 + 9430^2 .

It is a cyclic number.

It is not a de Polignac number, because 661904869 - 2¹¹ = 661902821 is a prime.

It is a super-2 number, since 2×661904869² = 876236111211814322, 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 (661904819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330952434 + 330952435.

It is an arithmetic number, because the mean of its divisors is an integer number (330952435).

Almost surely, 2^661904869 is an apocalyptic number.

It is an amenable number.

661904869 is a deficient number, since it is larger than the sum of its proper divisors (1).

661904869 is an equidigital number, since it uses as much as digits as its factorization.

661904869 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 559872, while the sum is 49.

The square root of 661904869 is about 25727.5119084610. The cubic root of 661904869 is about 871.4955862349.

The spelling of 661904869 in words is "six hundred sixty-one million, nine hundred four thousand, eight hundred sixty-nine".