51378021 has 12 divisors (see below), whose sum is σ = 77439648. Its totient is φ = 32762664.

The previous prime is 51378017. The next prime is 51378023. The reversal of 51378021 is 12087315.

It is not a de Polignac number, because 51378021 - 2² = 51378017 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51378023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 123895 + ... + 124308.

It is an arithmetic number, because the mean of its divisors is an integer number (6453304).

Almost surely, 2^51378021 is an apocalyptic number.

It is an amenable number.

51378021 is a deficient number, since it is larger than the sum of its proper divisors (26061627).

51378021 is a wasteful number, since it uses less digits than its factorization.

51378021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248232 (or 248229 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 51378021 is about 7167.8463292679. The cubic root of 51378021 is about 371.7569735936.

The spelling of 51378021 in words is "fifty-one million, three hundred seventy-eight thousand, twenty-one".