81511970 has 8 divisors (see below), whose sum is σ = 146721564. Its totient is φ = 32604784.

The previous prime is 81511943. The next prime is 81511979. The reversal of 81511970 is 7911518.

It can be written as a sum of positive squares in 2 ways, for example, as 79798489 + 1713481 = 8933^2 + 1309^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81511979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4075589 + ... + 4075608.

Almost surely, 2^81511970 is an apocalyptic number.

81511970 is a deficient number, since it is larger than the sum of its proper divisors (65209594).

81511970 is a wasteful number, since it uses less digits than its factorization.

81511970 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8151204.

The product of its (nonzero) digits is 2520, while the sum is 32.

The square root of 81511970 is about 9028.3979752778. The cubic root of 81511970 is about 433.5845479588.

The spelling of 81511970 in words is "eighty-one million, five hundred eleven thousand, nine hundred seventy".