51621209 has 2 divisors, whose sum is σ = 51621210. Its totient is φ = 51621208.

The previous prime is 51621161. The next prime is 51621217. The reversal of 51621209 is 90212615.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37393225 + 14227984 = 6115^2 + 3772^2 .

It is a cyclic number.

It is not a de Polignac number, because 51621209 - 2⁸ = 51620953 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (51621239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25810604 + 25810605.

It is an arithmetic number, because the mean of its divisors is an integer number (25810605).

Almost surely, 2^51621209 is an apocalyptic number.

It is an amenable number.

51621209 is a deficient number, since it is larger than the sum of its proper divisors (1).

51621209 is an equidigital number, since it uses as much as digits as its factorization.

51621209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 51621209 is about 7184.7901152365. The cubic root of 51621209 is about 372.3425973417.

The spelling of 51621209 in words is "fifty-one million, six hundred twenty-one thousand, two hundred nine".