20641561 has 8 divisors (see below), whose sum is σ = 21072384. Its totient is φ = 20214480.

The previous prime is 20641559. The next prime is 20641571. The reversal of 20641561 is 16514602.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20641561 - 2¹ = 20641559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20641541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11991 + ... + 13603.

It is an arithmetic number, because the mean of its divisors is an integer number (2634048).

Almost surely, 2^20641561 is an apocalyptic number.

It is an amenable number.

20641561 is a deficient number, since it is larger than the sum of its proper divisors (430823).

20641561 is a wasteful number, since it uses less digits than its factorization.

20641561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1871.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 20641561 is about 4543.2984713752. The cubic root of 20641561 is about 274.3137091006.

The spelling of 20641561 in words is "twenty million, six hundred forty-one thousand, five hundred sixty-one".