1661877645 has 16 divisors (see below), whose sum is σ = 2672786112. Its totient is φ = 881740800.

The previous prime is 1661877629. The next prime is 1661877647. The reversal of 1661877645 is 5467781661.

It is a happy number.

It is not a de Polignac number, because 1661877645 - 2⁴ = 1661877629 is a prime.

It is a super-3 number, since 3×1661877645³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661877647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 284131 + ... + 289920.

It is an arithmetic number, because the mean of its divisors is an integer number (167049132).

Almost surely, 2^1661877645 is an apocalyptic number.

1661877645 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1661877645 is a deficient number, since it is larger than the sum of its proper divisors (1010908467).

1661877645 is a wasteful number, since it uses less digits than its factorization.

1661877645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 574252.

The product of its digits is 1693440, while the sum is 51.

The square root of 1661877645 is about 40766.1335547044. The cubic root of 1661877645 is about 1184.4944094652.

The spelling of 1661877645 in words is "one billion, six hundred sixty-one million, eight hundred seventy-seven thousand, six hundred forty-five".