861251581 has 2 divisors, whose sum is σ = 861251582. Its totient is φ = 861251580.

The previous prime is 861251539. The next prime is 861251593. The reversal of 861251581 is 185152168.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 828864100 + 32387481 = 28790^2 + 5691^2 .

It is a cyclic number.

It is not a de Polignac number, because 861251581 - 2¹³ = 861243389 is a prime.

It is a super-2 number, since 2×861251581² = 1483508571549999122, which contains 22 as substring.

It is equal to p_44128585 and since 861251581 and 44128585 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 861251581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (861251081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430625790 + 430625791.

It is an arithmetic number, because the mean of its divisors is an integer number (430625791).

Almost surely, 2^861251581 is an apocalyptic number.

It is an amenable number.

861251581 is a deficient number, since it is larger than the sum of its proper divisors (1).

861251581 is an equidigital number, since it uses as much as digits as its factorization.

861251581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19200, while the sum is 37.

The square root of 861251581 is about 29347.0881179036. The cubic root of 861251581 is about 951.4296410115.

The spelling of 861251581 in words is "eight hundred sixty-one million, two hundred fifty-one thousand, five hundred eighty-one".