51639949 has 4 divisors (see below), whose sum is σ = 52113820. Its totient is φ = 51166080.

The previous prime is 51639919. The next prime is 51639961. The reversal of 51639949 is 94993615.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 42380100 + 9259849 = 6510^2 + 3043^2 .

It is a cyclic number.

It is not a de Polignac number, because 51639949 - 2²⁵ = 18085517 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 51639899 and 51639908.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51639919) 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, 236772 + ... + 236989.

It is an arithmetic number, because the mean of its divisors is an integer number (13028455).

Almost surely, 2^51639949 is an apocalyptic number.

It is an amenable number.

51639949 is a deficient number, since it is larger than the sum of its proper divisors (473871).

51639949 is a wasteful number, since it uses less digits than its factorization.

51639949 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 473870.

The product of its digits is 262440, while the sum is 46.

The square root of 51639949 is about 7186.0941407694. The cubic root of 51639949 is about 372.3876489539.

It can be divided in two parts, 51 and 639949, that added together give a square (640000 = 800²).

The spelling of 51639949 in words is "fifty-one million, six hundred thirty-nine thousand, nine hundred forty-nine".