81972938 has 4 divisors (see below), whose sum is σ = 122959410. Its totient is φ = 40986468.

The previous prime is 81972911. The next prime is 81972949. The reversal of 81972938 is 83927918.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 81956809 + 16129 = 9053^2 + 127^2 .

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 81972892 and 81972901.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20493233 + ... + 20493236.

Almost surely, 2^81972938 is an apocalyptic number.

81972938 is a deficient number, since it is larger than the sum of its proper divisors (40986472).

81972938 is a wasteful number, since it uses less digits than its factorization.

81972938 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40986471.

The product of its digits is 217728, while the sum is 47.

The square root of 81972938 is about 9053.8907658531. The cubic root of 81972938 is about 434.4003504899.

The spelling of 81972938 in words is "eighty-one million, nine hundred seventy-two thousand, nine hundred thirty-eight".