21634100205721 has 2 divisors, whose sum is σ = 21634100205722. Its totient is φ = 21634100205720.

The previous prime is 21634100205713. The next prime is 21634100205737. The reversal of 21634100205721 is 12750200143612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19048642025625 + 2585458180096 = 4364475^2 + 1607936^2 .

It is a cyclic number.

It is not a de Polignac number, because 21634100205721 - 2³ = 21634100205713 is a prime.

It is a super-2 number, since 2×21634100205721² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21634100202721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10817050102860 + 10817050102861.

It is an arithmetic number, because the mean of its divisors is an integer number (10817050102861).

Almost surely, 2^{21634100205721} is an apocalyptic number.

It is an amenable number.

21634100205721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21634100205721 is an equidigital number, since it uses as much as digits as its factorization.

21634100205721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20160, while the sum is 34.

The spelling of 21634100205721 in words is "twenty-one trillion, six hundred thirty-four billion, one hundred million, two hundred five thousand, seven hundred twenty-one".