81207972 has 36 divisors (see below), whose sum is σ = 211900416. Its totient is φ = 26195760.

The previous prime is 81207967. The next prime is 81207977. The reversal of 81207972 is 27970218.

It is an interprime number because it is at equal distance from previous prime (81207967) and next prime (81207977).

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81207977) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35268 + ... + 37499.

Almost surely, 2^81207972 is an apocalyptic number.

It is an amenable number.

81207972 is an abundant number, since it is smaller than the sum of its proper divisors (130692444).

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

81207972 is a wasteful number, since it uses less digits than its factorization.

81207972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72808 (or 72803 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 81207972 is about 9011.5465931215. The cubic root of 81207972 is about 433.0448602065.

The spelling of 81207972 in words is "eighty-one million, two hundred seven thousand, nine hundred seventy-two".