1625055778666 has 4 divisors (see below), whose sum is σ = 2437583668002. Its totient is φ = 812527889332.

The previous prime is 1625055778663. The next prime is 1625055778699. The reversal of 1625055778666 is 6668775505261.

It is a happy number.

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., 1029573473041 + 595482305625 = 1014679^2 + 771675^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1625055778598 and 1625055778607.

It is not an unprimeable number, because it can be changed into a prime (1625055778663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 406263944665 + ... + 406263944668.

Almost surely, 2^{1625055778666} is an apocalyptic number.

1625055778666 is a deficient number, since it is larger than the sum of its proper divisors (812527889336).

1625055778666 is an equidigital number, since it uses as much as digits as its factorization.

1625055778666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 812527889335.

The product of its (nonzero) digits is 127008000, while the sum is 64.

The spelling of 1625055778666 in words is "one trillion, six hundred twenty-five billion, fifty-five million, seven hundred seventy-eight thousand, six hundred sixty-six".