81151988 has 6 divisors (see below), whose sum is σ = 142015986. Its totient is φ = 40575992.

The previous prime is 81151979. The next prime is 81152003. The reversal of 81151988 is 88915118.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 47720464 + 33431524 = 6908^2 + 5782^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10143995 + ... + 10144002.

It is an arithmetic number, because the mean of its divisors is an integer number (23669331).

Almost surely, 2^81151988 is an apocalyptic number.

It is an amenable number.

81151988 is a deficient number, since it is larger than the sum of its proper divisors (60863998).

81151988 is a wasteful number, since it uses less digits than its factorization.

81151988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20288001 (or 20287999 counting only the distinct ones).

The product of its digits is 23040, while the sum is 41.

The square root of 81151988 is about 9008.4398205239. The cubic root of 81151988 is about 432.9453250004.

The spelling of 81151988 in words is "eighty-one million, one hundred fifty-one thousand, nine hundred eighty-eight".