81669987 has 48 divisors (see below), whose sum is σ = 141972480. Its totient is φ = 44231616.

The previous prime is 81669977. The next prime is 81670007. The reversal of 81669987 is 78996618.

It is not a de Polignac number, because 81669987 - 2⁴ = 81669971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81669937) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 227314 + ... + 227672.

It is an arithmetic number, because the mean of its divisors is an integer number (2957760).

Almost surely, 2^81669987 is an apocalyptic number.

81669987 is a deficient number, since it is larger than the sum of its proper divisors (60302493).

81669987 is a wasteful number, since it uses less digits than its factorization.

81669987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 552 (or 549 counting only the distinct ones).

The product of its digits is 1306368, while the sum is 54.

The square root of 81669987 is about 9037.1448477935. The cubic root of 81669987 is about 433.8645457070.

The spelling of 81669987 in words is "eighty-one million, six hundred sixty-nine thousand, nine hundred eighty-seven".