1654561661 has 4 divisors (see below), whose sum is σ = 1657851552. Its totient is φ = 1651271772.

The previous prime is 1654561627. The next prime is 1654561673. The reversal of 1654561661 is 1661654561.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1661654561 = 7 ⋅237379223.

It is a cyclic number.

It is not a de Polignac number, because 1654561661 - 2²² = 1650367357 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 (1654561681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1644191 + ... + 1645196.

It is an arithmetic number, because the mean of its divisors is an integer number (414462888).

Almost surely, 2^1654561661 is an apocalyptic number.

It is an amenable number.

1654561661 is a deficient number, since it is larger than the sum of its proper divisors (3289891).

1654561661 is an equidigital number, since it uses as much as digits as its factorization.

1654561661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3289890.

The product of its digits is 129600, while the sum is 41.

The square root of 1654561661 is about 40676.3034333259. The cubic root of 1654561661 is about 1182.7537098033.

The spelling of 1654561661 in words is "one billion, six hundred fifty-four million, five hundred sixty-one thousand, six hundred sixty-one".