1661357531 has 4 divisors (see below), whose sum is σ = 1661457864. Its totient is φ = 1661257200.

The previous prime is 1661357513. The next prime is 1661357543. The reversal of 1661357531 is 1357531661.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1357531661 = 3511 ⋅386651.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661357531 is a prime.

It is a super-2 number, since 2×1661357531² = 5520217691620831922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661357501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18785 + ... + 60626.

It is an arithmetic number, because the mean of its divisors is an integer number (415364466).

Almost surely, 2^1661357531 is an apocalyptic number.

1661357531 is a deficient number, since it is larger than the sum of its proper divisors (100333).

1661357531 is an equidigital number, since it uses as much as digits as its factorization.

1661357531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100332.

The product of its digits is 56700, while the sum is 38.

The square root of 1661357531 is about 40759.7538142713. The cubic root of 1661357531 is about 1184.3708270806.

The spelling of 1661357531 in words is "one billion, six hundred sixty-one million, three hundred fifty-seven thousand, five hundred thirty-one".