81787976 has 8 divisors (see below), whose sum is σ = 153352470. Its totient is φ = 40893984.

The previous prime is 81787963. The next prime is 81787991. The reversal of 81787976 is 67978718.

It can be written as a sum of positive squares in only one way, i.e., 63520900 + 18267076 = 7970^2 + 4274^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5111741 + ... + 5111756.

Almost surely, 2^81787976 is an apocalyptic number.

It is an amenable number.

81787976 is a deficient number, since it is larger than the sum of its proper divisors (71564494).

81787976 is a wasteful number, since it uses less digits than its factorization.

81787976 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10223503 (or 10223499 counting only the distinct ones).

The product of its digits is 1185408, while the sum is 53.

The square root of 81787976 is about 9043.6704937763. The cubic root of 81787976 is about 434.0733805289.

The spelling of 81787976 in words is "eighty-one million, seven hundred eighty-seven thousand, nine hundred seventy-six".