81651445 has 4 divisors (see below), whose sum is σ = 97981740. Its totient is φ = 65321152.

The previous prime is 81651433. The next prime is 81651467. The reversal of 81651445 is 54415618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54415618 = 2 ⋅27207809.

It can be written as a sum of positive squares in 2 ways, for example, as 40780996 + 40870449 = 6386^2 + 6393^2 .

It is a cyclic number.

It is not a de Polignac number, because 81651445 - 2⁵ = 81651413 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81651445.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8165140 + ... + 8165149.

It is an arithmetic number, because the mean of its divisors is an integer number (24495435).

Almost surely, 2^81651445 is an apocalyptic number.

It is an amenable number.

81651445 is a deficient number, since it is larger than the sum of its proper divisors (16330295).

81651445 is a wasteful number, since it uses less digits than its factorization.

81651445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16330294.

The product of its digits is 19200, while the sum is 34.

The square root of 81651445 is about 9036.1189124535. The cubic root of 81651445 is about 433.8317089796.

The spelling of 81651445 in words is "eighty-one million, six hundred fifty-one thousand, four hundred forty-five".