20261578561 has 16 divisors (see below), whose sum is σ = 23341680640. Its totient is φ = 17228427840.

The previous prime is 20261578559. The next prime is 20261578591. The reversal of 20261578561 is 16587516202.

It is a cyclic number.

It is not a de Polignac number, because 20261578561 - 2¹ = 20261578559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20261578591) 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 15 ways as a sum of consecutive naturals, for example, 421216 + ... + 466846.

It is an arithmetic number, because the mean of its divisors is an integer number (1458855040).

Almost surely, 2^20261578561 is an apocalyptic number.

It is an amenable number.

20261578561 is a deficient number, since it is larger than the sum of its proper divisors (3080102079).

20261578561 is a wasteful number, since it uses less digits than its factorization.

20261578561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46144.

The product of its (nonzero) digits is 201600, while the sum is 43.

The spelling of 20261578561 in words is "twenty billion, two hundred sixty-one million, five hundred seventy-eight thousand, five hundred sixty-one".