81690385 has 16 divisors (see below), whose sum is σ = 112179456. Its totient is φ = 55942848.

The previous prime is 81690379. The next prime is 81690403. The reversal of 81690385 is 58309618.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 81690385 - 2¹¹ = 81688337 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49839 + ... + 51451.

It is an arithmetic number, because the mean of its divisors is an integer number (7011216).

Almost surely, 2^81690385 is an apocalyptic number.

It is an amenable number.

81690385 is a deficient number, since it is larger than the sum of its proper divisors (30489071).

81690385 is a wasteful number, since it uses less digits than its factorization.

With its successor (81690386) it forms an eRAP, since the sums of their prime factors are consecutive (3072 and 3073).

81690385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3072.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 81690385 is about 9038.2733417396. The cubic root of 81690385 is about 433.9006635541.

The spelling of 81690385 in words is "eighty-one million, six hundred ninety thousand, three hundred eighty-five".