81437709 has 4 divisors (see below), whose sum is σ = 108583616. Its totient is φ = 54291804.

The previous prime is 81437693. The next prime is 81437729. The reversal of 81437709 is 90773418.

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 not a de Polignac number, because 81437709 - 2⁴ = 81437693 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 (81437729) 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, 13572949 + ... + 13572954.

It is an arithmetic number, because the mean of its divisors is an integer number (27145904).

Almost surely, 2^81437709 is an apocalyptic number.

It is an amenable number.

81437709 is a deficient number, since it is larger than the sum of its proper divisors (27145907).

81437709 is a wasteful number, since it uses less digits than its factorization.

81437709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27145906.

The product of its (nonzero) digits is 42336, while the sum is 39.

The square root of 81437709 is about 9024.2844037630. The cubic root of 81437709 is about 433.4528364031.

The spelling of 81437709 in words is "eighty-one million, four hundred thirty-seven thousand, seven hundred nine".