21215715057553 has 2 divisors, whose sum is σ = 21215715057554. Its totient is φ = 21215715057552.

The previous prime is 21215715057539. The next prime is 21215715057557. The reversal of 21215715057553 is 35575051751212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18622400975424 + 2593314082129 = 4315368^2 + 1610377^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21215715057553 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21215715057497 and 21215715057506.

It is not a weakly prime, because it can be changed into another prime (21215715057557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607857528776 + 10607857528777.

It is an arithmetic number, because the mean of its divisors is an integer number (10607857528777).

Almost surely, 2^{21215715057553} is an apocalyptic number.

It is an amenable number.

21215715057553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21215715057553 is an equidigital number, since it uses as much as digits as its factorization.

21215715057553 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1837500, while the sum is 49.

The spelling of 21215715057553 in words is "twenty-one trillion, two hundred fifteen billion, seven hundred fifteen million, fifty-seven thousand, five hundred fifty-three".