51720789 has 4 divisors (see below), whose sum is σ = 68961056. Its totient is φ = 34480524.

The previous prime is 51720751. The next prime is 51720811. The reversal of 51720789 is 98702715.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 51720789 - 2¹⁹ = 51196501 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51720089) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8620129 + ... + 8620134.

It is an arithmetic number, because the mean of its divisors is an integer number (17240264).

Almost surely, 2^51720789 is an apocalyptic number.

It is an amenable number.

51720789 is a deficient number, since it is larger than the sum of its proper divisors (17240267).

51720789 is a wasteful number, since it uses less digits than its factorization.

51720789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17240266.

The product of its (nonzero) digits is 35280, while the sum is 39.

The square root of 51720789 is about 7191.7166935301. The cubic root of 51720789 is about 372.5818663060.

The spelling of 51720789 in words is "fifty-one million, seven hundred twenty thousand, seven hundred eighty-nine".