21612520185397 has 2 divisors, whose sum is σ = 21612520185398. Its totient is φ = 21612520185396.

The previous prime is 21612520185383. The next prime is 21612520185419. The reversal of 21612520185397 is 79358102521612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20594814498801 + 1017705686596 = 4538151^2 + 1008814^2 .

It is a cyclic number.

It is not a de Polignac number, because 21612520185397 - 2²³ = 21612511796789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21612520185307) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806260092698 + 10806260092699.

It is an arithmetic number, because the mean of its divisors is an integer number (10806260092699).

Almost surely, 2^{21612520185397} is an apocalyptic number.

It is an amenable number.

21612520185397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612520185397 is an equidigital number, since it uses as much as digits as its factorization.

21612520185397 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1814400, while the sum is 52.

The spelling of 21612520185397 in words is "twenty-one trillion, six hundred twelve billion, five hundred twenty million, one hundred eighty-five thousand, three hundred ninety-seven".