51489721 has 2 divisors, whose sum is σ = 51489722. Its totient is φ = 51489720.

The previous prime is 51489689. The next prime is 51489731. The reversal of 51489721 is 12798415.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 40500496 + 10989225 = 6364^2 + 3315^2 .

It is a cyclic number.

It is not a de Polignac number, because 51489721 - 2⁵ = 51489689 is a prime.

It is not a weakly prime, because it can be changed into another prime (51489731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25744860 + 25744861.

It is an arithmetic number, because the mean of its divisors is an integer number (25744861).

Almost surely, 2^51489721 is an apocalyptic number.

It is an amenable number.

51489721 is a deficient number, since it is larger than the sum of its proper divisors (1).

51489721 is an equidigital number, since it uses as much as digits as its factorization.

51489721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20160, while the sum is 37.

The square root of 51489721 is about 7175.6338395991. The cubic root of 51489721 is about 372.0261885637.

The spelling of 51489721 in words is "fifty-one million, four hundred eighty-nine thousand, seven hundred twenty-one".