21306356551 has 2 divisors, whose sum is σ = 21306356552. Its totient is φ = 21306356550.

The previous prime is 21306356503. The next prime is 21306356563. The reversal of 21306356551 is 15565360312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21306356551 - 2²⁵ = 21272802119 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21306356551.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21306350551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10653178275 + 10653178276.

It is an arithmetic number, because the mean of its divisors is an integer number (10653178276).

Almost surely, 2^21306356551 is an apocalyptic number.

21306356551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21306356551 is an equidigital number, since it uses as much as digits as its factorization.

21306356551 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 81000, while the sum is 37.

The spelling of 21306356551 in words is "twenty-one billion, three hundred six million, three hundred fifty-six thousand, five hundred fifty-one".