21255563601 has 12 divisors (see below), whose sum is σ = 31761187380. Its totient is φ = 13681741920.

The previous prime is 21255563507. The next prime is 21255563611. The reversal of 21255563601 is 10636555212.

21255563601 is a `hidden beast` number, since 2 + 12 + 5 + 5 + 5 + 636 + 0 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 14195531025 + 7060032576 = 119145^2 + 84024^2 .

It is not a de Polignac number, because 21255563601 - 2¹⁵ = 21255530833 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21255563611) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 40719210 + ... + 40719731.

It is an arithmetic number, because the mean of its divisors is an integer number (2646765615).

Almost surely, 2^21255563601 is an apocalyptic number.

It is an amenable number.

21255563601 is a deficient number, since it is larger than the sum of its proper divisors (10505623779).

21255563601 is a wasteful number, since it uses less digits than its factorization.

21255563601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81438976 (or 81438973 counting only the distinct ones).

The product of its (nonzero) digits is 54000, while the sum is 36.

The spelling of 21255563601 in words is "twenty-one billion, two hundred fifty-five million, five hundred sixty-three thousand, six hundred one".