78211691 has 2 divisors, whose sum is σ = 78211692. Its totient is φ = 78211690.

The previous prime is 78211681. The next prime is 78211697. The reversal of 78211691 is 19611287.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78211691 - 2²² = 74017387 is a prime.

It is a super-2 number, since 2×78211691² = 12234137218158962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78211697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39105845 + 39105846.

It is an arithmetic number, because the mean of its divisors is an integer number (39105846).

Almost surely, 2^78211691 is an apocalyptic number.

78211691 is a deficient number, since it is larger than the sum of its proper divisors (1).

78211691 is an equidigital number, since it uses as much as digits as its factorization.

78211691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 35.

The square root of 78211691 is about 8843.7373886836. The cubic root of 78211691 is about 427.6520503785.

The spelling of 78211691 in words is "seventy-eight million, two hundred eleven thousand, six hundred ninety-one".