20561601655 has 16 divisors (see below), whose sum is σ = 28211920704. Its totient is φ = 14092807680.

The previous prime is 20561601611. The next prime is 20561601673. The reversal of 20561601655 is 55610616502.

It is not a de Polignac number, because 20561601655 - 2¹⁵ = 20561568887 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 60292 + ... + 211561.

It is an arithmetic number, because the mean of its divisors is an integer number (1763245044).

Almost surely, 2^20561601655 is an apocalyptic number.

20561601655 is a deficient number, since it is larger than the sum of its proper divisors (7650319049).

20561601655 is a wasteful number, since it uses less digits than its factorization.

20561601655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274026.

The product of its (nonzero) digits is 54000, while the sum is 37.

The spelling of 20561601655 in words is "twenty billion, five hundred sixty-one million, six hundred one thousand, six hundred fifty-five".