21476137721 has 2 divisors, whose sum is σ = 21476137722. Its totient is φ = 21476137720.

The previous prime is 21476137699. The next prime is 21476137729. The reversal of 21476137721 is 12773167412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20373565696 + 1102572025 = 142736^2 + 33205^2 .

It is a cyclic number.

It is not a de Polignac number, because 21476137721 - 2¹⁰ = 21476136697 is a prime.

It is a super-2 number, since 2×21476137721² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21476137729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10738068860 + 10738068861.

It is an arithmetic number, because the mean of its divisors is an integer number (10738068861).

Almost surely, 2^21476137721 is an apocalyptic number.

It is an amenable number.

21476137721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21476137721 is an equidigital number, since it uses as much as digits as its factorization.

21476137721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 98784, while the sum is 41.

The spelling of 21476137721 in words is "twenty-one billion, four hundred seventy-six million, one hundred thirty-seven thousand, seven hundred twenty-one".