21531333555551 has 2 divisors, whose sum is σ = 21531333555552. Its totient is φ = 21531333555550.

The previous prime is 21531333555547. The next prime is 21531333555569. The reversal of 21531333555551 is 15555533313512.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21531333555551 - 2² = 21531333555547 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21531333555496 and 21531333555505.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21531333515551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765666777775 + 10765666777776.

It is an arithmetic number, because the mean of its divisors is an integer number (10765666777776).

Almost surely, 2^{21531333555551} is an apocalyptic number.

21531333555551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531333555551 is an equidigital number, since it uses as much as digits as its factorization.

21531333555551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2531250, while the sum is 47.

The spelling of 21531333555551 in words is "twenty-one trillion, five hundred thirty-one billion, three hundred thirty-three million, five hundred fifty-five thousand, five hundred fifty-one".