81651988 has 48 divisors (see below), whose sum is σ = 161118720. Its totient is φ = 35890400.

The previous prime is 81651979. The next prime is 81652049. The reversal of 81651988 is 88915618.

It is a congruent 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, 184095 + ... + 184537.

It is an arithmetic number, because the mean of its divisors is an integer number (3356640).

Almost surely, 2^81651988 is an apocalyptic number.

It is an amenable number.

81651988 is a deficient number, since it is larger than the sum of its proper divisors (79466732).

81651988 is a wasteful number, since it uses less digits than its factorization.

81651988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 588 (or 586 counting only the distinct ones).

The product of its digits is 138240, while the sum is 46.

The square root of 81651988 is about 9036.1489584889. The cubic root of 81651988 is about 433.8326706695.

It can be divided in two parts, 8165 and 1988, that added together give a triangular number (10153 = T₁₄₂).

The spelling of 81651988 in words is "eighty-one million, six hundred fifty-one thousand, nine hundred eighty-eight".