81219825 has 18 divisors (see below), whose sum is σ = 145474134. Its totient is φ = 43317120.

The previous prime is 81219793. The next prime is 81219841. The reversal of 81219825 is 52891218.

It can be written as a sum of positive squares in 3 ways, for example, as 651249 + 80568576 = 807^2 + 8976^2 .

It is not a de Polignac number, because 81219825 - 2⁵ = 81219793 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81219825.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 180264 + ... + 180713.

Almost surely, 2^81219825 is an apocalyptic number.

It is an amenable number.

81219825 is a deficient number, since it is larger than the sum of its proper divisors (64254309).

81219825 is a wasteful number, since it uses less digits than its factorization.

81219825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360993 (or 360985 counting only the distinct ones).

The product of its digits is 11520, while the sum is 36.

The square root of 81219825 is about 9012.2042253824. The cubic root of 81219825 is about 433.0659280520.

The spelling of 81219825 in words is "eighty-one million, two hundred nineteen thousand, eight hundred twenty-five".