21820950001957 has 2 divisors, whose sum is σ = 21820950001958. Its totient is φ = 21820950001956.

The previous prime is 21820950001951. The next prime is 21820950002017. The reversal of 21820950001957 is 75910005902812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19458209033316 + 2362740968641 = 4411146^2 + 1537121^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21820950001957 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21820950001957.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21820950001951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10910475000978 + 10910475000979.

It is an arithmetic number, because the mean of its divisors is an integer number (10910475000979).

Almost surely, 2^{21820950001957} is an apocalyptic number.

It is an amenable number.

21820950001957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21820950001957 is an equidigital number, since it uses as much as digits as its factorization.

21820950001957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 453600, while the sum is 49.

The spelling of 21820950001957 in words is "twenty-one trillion, eight hundred twenty billion, nine hundred fifty million, one thousand, nine hundred fifty-seven".