81553251 has 16 divisors (see below), whose sum is σ = 117331200. Its totient is φ = 50088480.

The previous prime is 81553243. The next prime is 81553259. The reversal of 81553251 is 15235518.

It is an interprime number because it is at equal distance from previous prime (81553243) and next prime (81553259).

It is not a de Polignac number, because 81553251 - 2³ = 81553243 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81553259) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21616 + ... + 25106.

It is an arithmetic number, because the mean of its divisors is an integer number (7333200).

Almost surely, 2^81553251 is an apocalyptic number.

81553251 is a deficient number, since it is larger than the sum of its proper divisors (35777949).

81553251 is a wasteful number, since it uses less digits than its factorization.

81553251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4106.

The product of its digits is 6000, while the sum is 30.

The square root of 81553251 is about 9030.6838611481. The cubic root of 81553251 is about 433.6577305969.

Adding to 81553251 its reverse (15235518), we get a palindrome (96788769).

The spelling of 81553251 in words is "eighty-one million, five hundred fifty-three thousand, two hundred fifty-one".