81121957 has 4 divisors (see below), whose sum is σ = 92710816. Its totient is φ = 69533100.

The previous prime is 81121939. The next prime is 81121967. The reversal of 81121957 is 75912118.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81121957 - 2⁷ = 81121829 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81121927) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5794419 + ... + 5794432.

It is an arithmetic number, because the mean of its divisors is an integer number (23177704).

Almost surely, 2^81121957 is an apocalyptic number.

It is an amenable number.

81121957 is a deficient number, since it is larger than the sum of its proper divisors (11588859).

81121957 is a wasteful number, since it uses less digits than its factorization.

81121957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11588858.

The product of its digits is 5040, while the sum is 34.

The square root of 81121957 is about 9006.7728404795. The cubic root of 81121957 is about 432.8919133485.

The spelling of 81121957 in words is "eighty-one million, one hundred twenty-one thousand, nine hundred fifty-seven".