1661897653 has 4 divisors (see below), whose sum is σ = 1789735948. Its totient is φ = 1534059360.

The previous prime is 1661897651. The next prime is 1661897689. The reversal of 1661897653 is 3567981661.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3567981661 = 107 ⋅33345623.

It can be written as a sum of positive squares in 2 ways, for example, as 402925329 + 1258972324 = 20073^2 + 35482^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661897653 - 2¹ = 1661897651 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1661897653.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661897651) 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, 63919128 + ... + 63919153.

It is an arithmetic number, because the mean of its divisors is an integer number (447433987).

Almost surely, 2^1661897653 is an apocalyptic number.

1661897653 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

1661897653 is a deficient number, since it is larger than the sum of its proper divisors (127838295).

1661897653 is a wasteful number, since it uses less digits than its factorization.

1661897653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127838294.

The product of its digits is 1632960, while the sum is 52.

The square root of 1661897653 is about 40766.3789537408. The cubic root of 1661897653 is about 1184.4991629778.

The spelling of 1661897653 in words is "one billion, six hundred sixty-one million, eight hundred ninety-seven thousand, six hundred fifty-three".