21506076012721 has 2 divisors, whose sum is σ = 21506076012722. Its totient is φ = 21506076012720.

The previous prime is 21506076012691. The next prime is 21506076012761. The reversal of 21506076012721 is 12721067060512.

It is an a-pointer prime, because the next prime (21506076012761) can be obtained adding 21506076012721 to its sum of digits (40).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20660115715600 + 845960297121 = 4545340^2 + 919761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506076012721 - 2⁹ = 21506076012209 is a prime.

It is a super-2 number, since 2×21506076012721² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21506076012761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753038006360 + 10753038006361.

It is an arithmetic number, because the mean of its divisors is an integer number (10753038006361).

Almost surely, 2^{21506076012721} is an apocalyptic number.

It is an amenable number.

21506076012721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506076012721 is an equidigital number, since it uses as much as digits as its factorization.

21506076012721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 70560, while the sum is 40.

The spelling of 21506076012721 in words is "twenty-one trillion, five hundred six billion, seventy-six million, twelve thousand, seven hundred twenty-one".