81956749 has 4 divisors (see below), whose sum is σ = 93664864. Its totient is φ = 70248636.

The previous prime is 81956731. The next prime is 81956759. The reversal of 81956749 is 94765918.

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 a cyclic number.

It is not a de Polignac number, because 81956749 - 2⁷ = 81956621 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 (81956759) 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, 5854047 + ... + 5854060.

It is an arithmetic number, because the mean of its divisors is an integer number (23416216).

Almost surely, 2^81956749 is an apocalyptic number.

It is an amenable number.

81956749 is a deficient number, since it is larger than the sum of its proper divisors (11708115).

81956749 is a wasteful number, since it uses less digits than its factorization.

81956749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11708114.

The product of its digits is 544320, while the sum is 49.

The square root of 81956749 is about 9052.9966861808. The cubic root of 81956749 is about 434.3717517415.

The spelling of 81956749 in words is "eighty-one million, nine hundred fifty-six thousand, seven hundred forty-nine".