21555125797 has 2 divisors, whose sum is σ = 21555125798. Its totient is φ = 21555125796.

The previous prime is 21555125783. The next prime is 21555125807. The reversal of 21555125797 is 79752155512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16766624196 + 4788501601 = 129486^2 + 69199^2 .

It is a cyclic number.

It is not a de Polignac number, because 21555125797 - 2²³ = 21546737189 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21555125797.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21555425797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10777562898 + 10777562899.

It is an arithmetic number, because the mean of its divisors is an integer number (10777562899).

Almost surely, 2^21555125797 is an apocalyptic number.

It is an amenable number.

21555125797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21555125797 is an equidigital number, since it uses as much as digits as its factorization.

21555125797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1102500, while the sum is 49.

The spelling of 21555125797 in words is "twenty-one billion, five hundred fifty-five million, one hundred twenty-five thousand, seven hundred ninety-seven".