21655420606531 has 4 divisors (see below), whose sum is σ = 21655439471952. Its totient is φ = 21655401741112.

The previous prime is 21655420606513. The next prime is 21655420606621. The reversal of 21655420606531 is 13560602455612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21655420606531 - 2³⁹ = 21105664792643 is a prime.

It is a super-2 number, since 2×21655420606531² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21655420601531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7591015 + ... + 10046608.

It is an arithmetic number, because the mean of its divisors is an integer number (5413859867988).

Almost surely, 2^{21655420606531} is an apocalyptic number.

21655420606531 is a deficient number, since it is larger than the sum of its proper divisors (18865421).

21655420606531 is a wasteful number, since it uses less digits than its factorization.

21655420606531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18865420.

The product of its (nonzero) digits is 1296000, while the sum is 46.

The spelling of 21655420606531 in words is "twenty-one trillion, six hundred fifty-five billion, four hundred twenty million, six hundred six thousand, five hundred thirty-one".