21655101204251 has 32 divisors (see below), whose sum is σ = 23460895054080. Its totient is φ = 19910069452800.

The previous prime is 21655101204241. The next prime is 21655101204263. The reversal of 21655101204251 is 15240210155612.

It is a cyclic number.

It is not a de Polignac number, because 21655101204251 - 2¹⁸ = 21655100942107 is a prime.

It is a super-2 number, since 2×21655101204251² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21655101204221) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2421995441 + ... + 2422004381.

It is an arithmetic number, because the mean of its divisors is an integer number (733152970440).

Almost surely, 2^{21655101204251} is an apocalyptic number.

21655101204251 is a deficient number, since it is larger than the sum of its proper divisors (1805793849829).

21655101204251 is a wasteful number, since it uses less digits than its factorization.

21655101204251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14375.

The product of its (nonzero) digits is 24000, while the sum is 35.

Adding to 21655101204251 its reverse (15240210155612), we get a palindrome (36895311359863).

The spelling of 21655101204251 in words is "twenty-one trillion, six hundred fifty-five billion, one hundred one million, two hundred four thousand, two hundred fifty-one".