1661025645 has 48 divisors (see below), whose sum is σ = 2963134512. Its totient is φ = 860129280.

The previous prime is 1661025599. The next prime is 1661025677. The reversal of 1661025645 is 5465201661.

1661025645 is a `hidden beast` number, since 1 + 6 + 6 + 1 + 0 + 2 + 5 + 645 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 140493609 + 1520532036 = 11853^2 + 38994^2 .

It is not a de Polignac number, because 1661025645 - 2¹⁰ = 1661024621 is a prime.

It is a super-3 number, since 3×1661025645³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1219765 + ... + 1221125.

It is an arithmetic number, because the mean of its divisors is an integer number (61731969).

Almost surely, 2^1661025645 is an apocalyptic number.

1661025645 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1661025645 is a deficient number, since it is larger than the sum of its proper divisors (1302108867).

1661025645 is a wasteful number, since it uses less digits than its factorization.

1661025645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2142 (or 2139 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

The square root of 1661025645 is about 40755.6823645489. The cubic root of 1661025645 is about 1184.2919553815.

The spelling of 1661025645 in words is "one billion, six hundred sixty-one million, twenty-five thousand, six hundred forty-five".