21555155206291 has 12 divisors (see below), whose sum is σ = 25074485452920. Its totient is φ = 18475757989920.

The previous prime is 21555155206271. The next prime is 21555155206357. The reversal of 21555155206291 is 19260255155512.

It is not a de Polignac number, because 21555155206291 - 2¹⁵ = 21555155173523 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21555155206271) 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, 10429015 + ... + 12323743.

It is an arithmetic number, because the mean of its divisors is an integer number (2089540454410).

Almost surely, 2^{21555155206291} is an apocalyptic number.

21555155206291 is a deficient number, since it is larger than the sum of its proper divisors (3519330246629).

21555155206291 is a wasteful number, since it uses less digits than its factorization.

21555155206291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2126914 (or 2126907 counting only the distinct ones).

The product of its (nonzero) digits is 1350000, while the sum is 49.

The spelling of 21555155206291 in words is "twenty-one trillion, five hundred fifty-five billion, one hundred fifty-five million, two hundred six thousand, two hundred ninety-one".