21016254462821 has 2 divisors, whose sum is σ = 21016254462822. Its totient is φ = 21016254462820.

The previous prime is 21016254462767. The next prime is 21016254462923. The reversal of 21016254462821 is 12826445261012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14142969789796 + 6873284673025 = 3760714^2 + 2621695^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21016254462821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21016254461821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10508127231410 + 10508127231411.

It is an arithmetic number, because the mean of its divisors is an integer number (10508127231411).

Almost surely, 2^{21016254462821} is an apocalyptic number.

It is an amenable number.

21016254462821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21016254462821 is an equidigital number, since it uses as much as digits as its factorization.

21016254462821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 368640, while the sum is 44.

The spelling of 21016254462821 in words is "twenty-one trillion, sixteen billion, two hundred fifty-four million, four hundred sixty-two thousand, eight hundred twenty-one".