81407906 has 4 divisors (see below), whose sum is σ = 122111862. Its totient is φ = 40703952.

The previous prime is 81407903. The next prime is 81407939. The reversal of 81407906 is 60970418.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 60970418 = 2 ⋅30485209.

It can be written as a sum of positive squares in only one way, i.e., 53158681 + 28249225 = 7291^2 + 5315^2 .

It is not an unprimeable number, because it can be changed into a prime (81407903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20351975 + ... + 20351978.

Almost surely, 2^81407906 is an apocalyptic number.

81407906 is a deficient number, since it is larger than the sum of its proper divisors (40703956).

81407906 is a wasteful number, since it uses less digits than its factorization.

81407906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40703955.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 81407906 is about 9022.6329859969. The cubic root of 81407906 is about 433.3999543856.

The spelling of 81407906 in words is "eighty-one million, four hundred seven thousand, nine hundred six".