51021491 has 2 divisors, whose sum is σ = 51021492. Its totient is φ = 51021490.

The previous prime is 51021473. The next prime is 51021493. The reversal of 51021491 is 19412015.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 51021491 - 2⁶ = 51021427 is a prime.

Together with 51021493, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (51021493) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25510745 + 25510746.

It is an arithmetic number, because the mean of its divisors is an integer number (25510746).

Almost surely, 2^51021491 is an apocalyptic number.

51021491 is a deficient number, since it is larger than the sum of its proper divisors (1).

51021491 is an equidigital number, since it uses as much as digits as its factorization.

51021491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360, while the sum is 23.

The square root of 51021491 is about 7142.9329410264. The cubic root of 51021491 is about 370.8950597188.

The spelling of 51021491 in words is "fifty-one million, twenty-one thousand, four hundred ninety-one".