51665389 has 4 divisors (see below), whose sum is σ = 54384640. Its totient is φ = 48946140.

The previous prime is 51665387. The next prime is 51665399. The reversal of 51665389 is 98356615.

51665389 = 1640² + 1641² + ... + 1658².

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 a cyclic number.

It is not a de Polignac number, because 51665389 - 2¹ = 51665387 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 (51665387) 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, 1359597 + ... + 1359634.

It is an arithmetic number, because the mean of its divisors is an integer number (13596160).

Almost surely, 2^51665389 is an apocalyptic number.

It is an amenable number.

51665389 is a deficient number, since it is larger than the sum of its proper divisors (2719251).

51665389 is a wasteful number, since it uses less digits than its factorization.

51665389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2719250.

The product of its digits is 194400, while the sum is 43.

The square root of 51665389 is about 7187.8640081738. The cubic root of 51665389 is about 372.4487901615.

The spelling of 51665389 in words is "fifty-one million, six hundred sixty-five thousand, three hundred eighty-nine".