21355420332251 has 4 divisors (see below), whose sum is σ = 21595368875400. Its totient is φ = 21115471789104.

The previous prime is 21355420332217. The next prime is 21355420332307. The reversal of 21355420332251 is 15223302455312.

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 21355420332251 - 2¹⁰ = 21355420331227 is a prime.

It is a super-2 number, since 2×21355420332251² (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 (21355420332151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 119974271441 + ... + 119974271618.

It is an arithmetic number, because the mean of its divisors is an integer number (5398842218850).

Almost surely, 2^{21355420332251} is an apocalyptic number.

21355420332251 is a deficient number, since it is larger than the sum of its proper divisors (239948543149).

21355420332251 is an equidigital number, since it uses as much as digits as its factorization.

21355420332251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 239948543148.

The product of its (nonzero) digits is 216000, while the sum is 38.

Adding to 21355420332251 its reverse (15223302455312), we get a palindrome (36578722787563).

The spelling of 21355420332251 in words is "twenty-one trillion, three hundred fifty-five billion, four hundred twenty million, three hundred thirty-two thousand, two hundred fifty-one".