1661155857 has 20 divisors (see below), whose sum is σ = 2518524976. Its totient is φ = 1090904760.

The previous prime is 1661155829. The next prime is 1661155907. The reversal of 1661155857 is 7585511661.

It is a happy number.

1661155857 is a `hidden beast` number, since 1 + 6 + 61 + 1 + 5 + 585 + 7 = 666.

It is not a de Polignac number, because 1661155857 - 2²⁸ = 1392720401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661155157) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 147619 + ... + 158472.

Almost surely, 2^1661155857 is an apocalyptic number.

It is an amenable number.

1661155857 is a deficient number, since it is larger than the sum of its proper divisors (857369119).

1661155857 is an equidigital number, since it uses as much as digits as its factorization.

1661155857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 306170 (or 306161 counting only the distinct ones).

The product of its digits is 252000, while the sum is 45.

The square root of 1661155857 is about 40757.2798037357. The cubic root of 1661155857 is about 1184.3229011198.

The spelling of 1661155857 in words is "one billion, six hundred sixty-one million, one hundred fifty-five thousand, eight hundred fifty-seven".