20164633721 has 2 divisors, whose sum is σ = 20164633722. Its totient is φ = 20164633720.

The previous prime is 20164633681. The next prime is 20164633733. The reversal of 20164633721 is 12733646102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19717776400 + 446857321 = 140420^2 + 21139^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20164633721 is a prime.

It is a super-2 number, since 2×20164633721² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20164633921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10082316860 + 10082316861.

It is an arithmetic number, because the mean of its divisors is an integer number (10082316861).

Almost surely, 2^20164633721 is an apocalyptic number.

It is an amenable number.

20164633721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20164633721 is an equidigital number, since it uses as much as digits as its factorization.

20164633721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36288, while the sum is 35.

The spelling of 20164633721 in words is "twenty billion, one hundred sixty-four million, six hundred thirty-three thousand, seven hundred twenty-one".