1990660651666 has 4 divisors (see below), whose sum is σ = 2985990977502. Its totient is φ = 995330325832.

The previous prime is 1990660651643. The next prime is 1990660651669. The reversal of 1990660651666 is 6661560660991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 1306849080625 + 683811571041 = 1143175^2 + 826929^2 .

It is not an unprimeable number, because it can be changed into a prime (1990660651669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 497665162915 + ... + 497665162918.

Almost surely, 2^{1990660651666} is an apocalyptic number.

1990660651666 is a deficient number, since it is larger than the sum of its proper divisors (995330325836).

1990660651666 is an equidigital number, since it uses as much as digits as its factorization.

1990660651666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 995330325835.

The product of its (nonzero) digits is 18895680, while the sum is 61.

The spelling of 1990660651666 in words is "one trillion, nine hundred ninety billion, six hundred sixty million, six hundred fifty-one thousand, six hundred sixty-six".