81721434 has 16 divisors (see below), whose sum is σ = 164541600. Its totient is φ = 27057360.

The previous prime is 81721429. The next prime is 81721439. The reversal of 81721434 is 43412718.

It is an interprime number because it is at equal distance from previous prime (81721429) and next prime (81721439).

It is not an unprimeable number, because it can be changed into a prime (81721439) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44812 + ... + 46599.

It is an arithmetic number, because the mean of its divisors is an integer number (10283850).

Almost surely, 2^81721434 is an apocalyptic number.

81721434 is an abundant number, since it is smaller than the sum of its proper divisors (82820166).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81721434 is a wasteful number, since it uses less digits than its factorization.

81721434 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91565.

The product of its digits is 5376, while the sum is 30.

The square root of 81721434 is about 9039.9908185794. The cubic root of 81721434 is about 433.9556291221.

The spelling of 81721434 in words is "eighty-one million, seven hundred twenty-one thousand, four hundred thirty-four".