661001987 has 2 divisors, whose sum is σ = 661001988. Its totient is φ = 661001986.

The previous prime is 661001953. The next prime is 661002019. The reversal of 661001987 is 789100166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661001987 - 2⁶ = 661001923 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 661001987.

It is not a weakly prime, because it can be changed into another prime (661001087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330500993 + 330500994.

It is an arithmetic number, because the mean of its divisors is an integer number (330500994).

Almost surely, 2^661001987 is an apocalyptic number.

661001987 is a deficient number, since it is larger than the sum of its proper divisors (1).

661001987 is an equidigital number, since it uses as much as digits as its factorization.

661001987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 661001987 is about 25709.9589070072. The cubic root of 661001987 is about 871.0991467255.

The spelling of 661001987 in words is "six hundred sixty-one million, one thousand, nine hundred eighty-seven".