81749651 has 4 divisors (see below), whose sum is σ = 86558472. Its totient is φ = 76940832.

The previous prime is 81749641. The next prime is 81749663. The reversal of 81749651 is 15694718.

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

It is a cyclic number.

It is not a de Polignac number, because 81749651 - 2⁶ = 81749587 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81749599 and 81749608.

It is not an unprimeable number, because it can be changed into a prime (81749641) 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, 2404385 + ... + 2404418.

It is an arithmetic number, because the mean of its divisors is an integer number (21639618).

Almost surely, 2^81749651 is an apocalyptic number.

81749651 is a deficient number, since it is larger than the sum of its proper divisors (4808821).

81749651 is a wasteful number, since it uses less digits than its factorization.

81749651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4808820.

The product of its digits is 60480, while the sum is 41.

The square root of 81749651 is about 9041.5513602479. The cubic root of 81749651 is about 434.0055691698.

The spelling of 81749651 in words is "eighty-one million, seven hundred forty-nine thousand, six hundred fifty-one".