51921381 has 4 divisors (see below), whose sum is σ = 69228512. Its totient is φ = 34614252.

The previous prime is 51921371. The next prime is 51921409. The reversal of 51921381 is 18312915.

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 not a de Polignac number, because 51921381 - 2¹¹ = 51919333 is a prime.

It is a super-2 number, since 2×51921381² = 5391659609894322, 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 (51921341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8653561 + ... + 8653566.

It is an arithmetic number, because the mean of its divisors is an integer number (17307128).

Almost surely, 2^51921381 is an apocalyptic number.

It is an amenable number.

51921381 is a deficient number, since it is larger than the sum of its proper divisors (17307131).

51921381 is a wasteful number, since it uses less digits than its factorization.

51921381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17307130.

The product of its digits is 2160, while the sum is 30.

The square root of 51921381 is about 7205.6492420878. The cubic root of 51921381 is about 373.0629142032.

The spelling of 51921381 in words is "fifty-one million, nine hundred twenty-one thousand, three hundred eighty-one".