78211981 has 8 divisors (see below), whose sum is σ = 80471744. Its totient is φ = 75984480.

The previous prime is 78211963. The next prime is 78211997. The reversal of 78211981 is 18911287.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 78211981 - 2⁵ = 78211949 is a prime.

It is a super-2 number, since 2×78211981² = 12234227943888722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 78211981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78211921) 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, 3105 + ... + 12886.

It is an arithmetic number, because the mean of its divisors is an integer number (10058968).

Almost surely, 2^78211981 is an apocalyptic number.

It is an amenable number.

78211981 is a deficient number, since it is larger than the sum of its proper divisors (2259763).

78211981 is a wasteful number, since it uses less digits than its factorization.

78211981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16131.

The product of its digits is 8064, while the sum is 37.

The square root of 78211981 is about 8843.7537844515. The cubic root of 78211981 is about 427.6525789395.

The spelling of 78211981 in words is "seventy-eight million, two hundred eleven thousand, nine hundred eighty-one".