21205655601 has 16 divisors (see below), whose sum is σ = 30528669696. Its totient is φ = 13015552896.

The previous prime is 21205655593. The next prime is 21205655629. The reversal of 21205655601 is 10655650212.

It is not a de Polignac number, because 21205655601 - 2³ = 21205655593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21205655671) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 694900 + ... + 724773.

It is an arithmetic number, because the mean of its divisors is an integer number (1908041856).

Almost surely, 2^21205655601 is an apocalyptic number.

It is an amenable number.

21205655601 is a deficient number, since it is larger than the sum of its proper divisors (9323014095).

21205655601 is a wasteful number, since it uses less digits than its factorization.

21205655601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1420072.

The product of its (nonzero) digits is 18000, while the sum is 33.

The spelling of 21205655601 in words is "twenty-one billion, two hundred five million, six hundred fifty-five thousand, six hundred one".