51720135645 has 16 divisors (see below), whose sum is σ = 82986651072. Its totient is φ = 27505927680.

The previous prime is 51720135587. The next prime is 51720135647. The reversal of 51720135645 is 54653102715.

It is not a de Polignac number, because 51720135645 - 2⁷ = 51720135517 is a prime.

It is a super-2 number, since 2×51720135645² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51720135647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4878571 + ... + 4889160.

It is an arithmetic number, because the mean of its divisors is an integer number (5186665692).

Almost surely, 2^51720135645 is an apocalyptic number.

It is an amenable number.

51720135645 is a deficient number, since it is larger than the sum of its proper divisors (31266515427).

51720135645 is a wasteful number, since it uses less digits than its factorization.

51720135645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9768092.

The product of its (nonzero) digits is 126000, while the sum is 39.

The spelling of 51720135645 in words is "fifty-one billion, seven hundred twenty million, one hundred thirty-five thousand, six hundred forty-five".