1251565541 has 2 divisors, whose sum is σ = 1251565542. Its totient is φ = 1251565540.

The previous prime is 1251565537. The next prime is 1251565543. The reversal of 1251565541 is 1455651521.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 669308641 + 582256900 = 25871^2 + 24130^2 .

It is a cyclic number.

It is not a de Polignac number, because 1251565541 - 2² = 1251565537 is a prime.

Together with 1251565543, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1251565543) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 625782770 + 625782771.

It is an arithmetic number, because the mean of its divisors is an integer number (625782771).

Almost surely, 2^1251565541 is an apocalyptic number.

It is an amenable number.

1251565541 is a deficient number, since it is larger than the sum of its proper divisors (1).

1251565541 is an equidigital number, since it uses as much as digits as its factorization.

1251565541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30000, while the sum is 35.

The square root of 1251565541 is about 35377.4722245669. The cubic root of 1251565541 is about 1077.6668715128. Note that the first 3 decimals are identical.

The spelling of 1251565541 in words is "one billion, two hundred fifty-one million, five hundred sixty-five thousand, five hundred forty-one".