81251650 has 24 divisors (see below), whose sum is σ = 153984564. Its totient is φ = 31886400.

The previous prime is 81251641. The next prime is 81251659. The reversal of 81251650 is 5615218.

It is an interprime number because it is at equal distance from previous prime (81251641) and next prime (81251659).

It can be written as a sum of positive squares in 6 ways, for example, as 65593801 + 15657849 = 8099^2 + 3957^2 .

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (81251659) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12681 + ... + 17980.

Almost surely, 2^81251650 is an apocalyptic number.

81251650 is a deficient number, since it is larger than the sum of its proper divisors (72732914).

81251650 is a wasteful number, since it uses less digits than its factorization.

81251650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30726 (or 30721 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 81251650 is about 9013.9697137277. The cubic root of 81251650 is about 433.1224845368.

Adding to 81251650 its reverse (5615218), we get a palindrome (86866868).

The spelling of 81251650 in words is "eighty-one million, two hundred fifty-one thousand, six hundred fifty".