51043981 has 4 divisors (see below), whose sum is σ = 51084000. Its totient is φ = 51003964.

The previous prime is 51043963. The next prime is 51043987. The reversal of 51043981 is 18934015.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18934015 = 5 ⋅3786803.

It is a cyclic number.

It is not a de Polignac number, because 51043981 - 2²³ = 42655373 is a prime.

It is a super-2 number, since 2×51043981² = 5210975992656722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51043987) 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, 18031 + ... + 20668.

It is an arithmetic number, because the mean of its divisors is an integer number (12771000).

Almost surely, 2^51043981 is an apocalyptic number.

It is an amenable number.

51043981 is a deficient number, since it is larger than the sum of its proper divisors (40019).

51043981 is a wasteful number, since it uses less digits than its factorization.

51043981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40018.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 51043981 is about 7144.5070508748. The cubic root of 51043981 is about 370.9495478990.

Adding to 51043981 its reverse (18934015), we get a palindrome (69977996).

The spelling of 51043981 in words is "fifty-one million, forty-three thousand, nine hundred eighty-one".