212191691 has 4 divisors (see below), whose sum is σ = 212403000. Its totient is φ = 211980384.

The previous prime is 212191673. The next prime is 212191729. The reversal of 212191691 is 196191212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-212191691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (212191631) 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, 104141 + ... + 106158.

It is an arithmetic number, because the mean of its divisors is an integer number (53100750).

Almost surely, 2^212191691 is an apocalyptic number.

212191691 is a deficient number, since it is larger than the sum of its proper divisors (211309).

212191691 is a wasteful number, since it uses less digits than its factorization.

212191691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211308.

The product of its digits is 1944, while the sum is 32.

The square root of 212191691 is about 14566.8009871763. The cubic root of 212191691 is about 596.4528589383.

The spelling of 212191691 in words is "two hundred twelve million, one hundred ninety-one thousand, six hundred ninety-one".