1661516553 has 4 divisors (see below), whose sum is σ = 2215355408. Its totient is φ = 1107677700.

The previous prime is 1661516551. The next prime is 1661516569. The reversal of 1661516553 is 3556151661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1661516553 - 2¹ = 1661516551 is a prime.

It is a super-3 number, since 3×1661516553³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661516551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 276919423 + ... + 276919428.

It is an arithmetic number, because the mean of its divisors is an integer number (553838852).

Almost surely, 2^1661516553 is an apocalyptic number.

It is an amenable number.

1661516553 is a deficient number, since it is larger than the sum of its proper divisors (553838855).

1661516553 is an equidigital number, since it uses as much as digits as its factorization.

1661516553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553838854.

The product of its digits is 81000, while the sum is 39.

The square root of 1661516553 is about 40761.7044908576. The cubic root of 1661516553 is about 1184.4086144534.

The spelling of 1661516553 in words is "one billion, six hundred sixty-one million, five hundred sixteen thousand, five hundred fifty-three".