51865021 has 8 divisors (see below), whose sum is σ = 57781080. Its totient is φ = 46224192.

The previous prime is 51864979. The next prime is 51865031. The reversal of 51865021 is 12056815.

It can be written as a sum of positive squares in 4 ways, for example, as 5692996 + 46172025 = 2386^2 + 6795^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 51865021 - 2⁷ = 51864893 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 (51865031) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 68410 + ... + 69163.

It is an arithmetic number, because the mean of its divisors is an integer number (7222635).

Almost surely, 2^51865021 is an apocalyptic number.

It is an amenable number.

51865021 is a deficient number, since it is larger than the sum of its proper divisors (5916059).

51865021 is a wasteful number, since it uses less digits than its factorization.

51865021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137615.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 51865021 is about 7201.7373598320. The cubic root of 51865021 is about 372.9278803129.

It can be divided in two parts, 518650 and 21, that added together give a triangular number (518671 = T₁₀₁₈).

The spelling of 51865021 in words is "fifty-one million, eight hundred sixty-five thousand, twenty-one".