51861391 has 2 divisors, whose sum is σ = 51861392. Its totient is φ = 51861390.

The previous prime is 51861377. The next prime is 51861409. The reversal of 51861391 is 19316815.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 51861391 - 2¹³ = 51853199 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51861331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25930695 + 25930696.

It is an arithmetic number, because the mean of its divisors is an integer number (25930696).

Almost surely, 2^51861391 is an apocalyptic number.

51861391 is a deficient number, since it is larger than the sum of its proper divisors (1).

51861391 is an equidigital number, since it uses as much as digits as its factorization.

51861391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6480, while the sum is 34.

The square root of 51861391 is about 7201.4853329018. The cubic root of 51861391 is about 372.9191797812.

The spelling of 51861391 in words is "fifty-one million, eight hundred sixty-one thousand, three hundred ninety-one".