20154565661 has 4 divisors (see below), whose sum is σ = 20228937024. Its totient is φ = 20080194300.

The previous prime is 20154565637. The next prime is 20154565687. The reversal of 20154565661 is 16656545102.

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 a cyclic number.

It is not a de Polignac number, because 20154565661 - 2⁶ = 20154565597 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 (20154565601) 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, 37185275 + ... + 37185816.

It is an arithmetic number, because the mean of its divisors is an integer number (5057234256).

Almost surely, 2^20154565661 is an apocalyptic number.

It is an amenable number.

20154565661 is a deficient number, since it is larger than the sum of its proper divisors (74371363).

20154565661 is an equidigital number, since it uses as much as digits as its factorization.

20154565661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74371362.

The product of its (nonzero) digits is 216000, while the sum is 41.

The spelling of 20154565661 in words is "twenty billion, one hundred fifty-four million, five hundred sixty-five thousand, six hundred sixty-one".