1661254405 has 4 divisors (see below), whose sum is σ = 1993505292. Its totient is φ = 1329003520.

The previous prime is 1661254393. The next prime is 1661254409. The reversal of 1661254405 is 5044521661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5044521661 = 127 ⋅39720643.

It can be written as a sum of positive squares in 2 ways, for example, as 497557636 + 1163696769 = 22306^2 + 34113^2 .

It is not a de Polignac number, because 1661254405 - 2¹¹ = 1661252357 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661254409) 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, 166125436 + ... + 166125445.

It is an arithmetic number, because the mean of its divisors is an integer number (498376323).

Almost surely, 2^1661254405 is an apocalyptic number.

It is an amenable number.

1661254405 is a deficient number, since it is larger than the sum of its proper divisors (332250887).

1661254405 is an equidigital number, since it uses as much as digits as its factorization.

1661254405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332250886.

The product of its (nonzero) digits is 28800, while the sum is 34.

The square root of 1661254405 is about 40758.4887477443. The cubic root of 1661254405 is about 1184.3463206251.

It can be divided in two parts, 16612 and 54405, that added together give a palindrome (71017).

The spelling of 1661254405 in words is "one billion, six hundred sixty-one million, two hundred fifty-four thousand, four hundred five".