51723649921 has 2 divisors, whose sum is σ = 51723649922. Its totient is φ = 51723649920.

The previous prime is 51723649903. The next prime is 51723649951. The reversal of 51723649921 is 12994632715.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43384307521 + 8339342400 = 208289^2 + 91320^2 .

It is a cyclic number.

It is not a de Polignac number, because 51723649921 - 2²¹ = 51721552769 is a prime.

It is a super-2 number, since 2×51723649921² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (51723649951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25861824960 + 25861824961.

It is an arithmetic number, because the mean of its divisors is an integer number (25861824961).

Almost surely, 2^51723649921 is an apocalyptic number.

It is an amenable number.

51723649921 is a deficient number, since it is larger than the sum of its proper divisors (1).

51723649921 is an equidigital number, since it uses as much as digits as its factorization.

51723649921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 816480, while the sum is 49.

The spelling of 51723649921 in words is "fifty-one billion, seven hundred twenty-three million, six hundred forty-nine thousand, nine hundred twenty-one".