51639947 has 4 divisors (see below), whose sum is σ = 52840920. Its totient is φ = 50438976.

The previous prime is 51639919. The next prime is 51639961. The reversal of 51639947 is 74993615.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 74993615 = 5 ⋅14998723.

It is a cyclic number.

It is not a de Polignac number, because 51639947 - 2⁶ = 51639883 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 51639898 and 51639907.

It is not an unprimeable number, because it can be changed into a prime (51639997) 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, 600422 + ... + 600507.

It is an arithmetic number, because the mean of its divisors is an integer number (13210230).

Almost surely, 2^51639947 is an apocalyptic number.

51639947 is a deficient number, since it is larger than the sum of its proper divisors (1200973).

51639947 is a wasteful number, since it uses less digits than its factorization.

51639947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1200972.

The product of its digits is 204120, while the sum is 44.

The square root of 51639947 is about 7186.0940016117. The cubic root of 51639947 is about 372.3876441464.

The spelling of 51639947 in words is "fifty-one million, six hundred thirty-nine thousand, nine hundred forty-seven".