81407542 has 4 divisors (see below), whose sum is σ = 122111316. Its totient is φ = 40703770.

The previous prime is 81407539. The next prime is 81407549. The reversal of 81407542 is 24570418.

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

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81407549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20351884 + ... + 20351887.

It is an arithmetic number, because the mean of its divisors is an integer number (30527829).

Almost surely, 2^81407542 is an apocalyptic number.

81407542 is a deficient number, since it is larger than the sum of its proper divisors (40703774).

81407542 is a wasteful number, since it uses less digits than its factorization.

81407542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40703773.

The product of its (nonzero) digits is 8960, while the sum is 31.

The square root of 81407542 is about 9022.6128144790. The cubic root of 81407542 is about 433.3993084295.

The spelling of 81407542 in words is "eighty-one million, four hundred seven thousand, five hundred forty-two".