21966891 has 16 divisors (see below), whose sum is σ = 30650400. Its totient is φ = 13975808.

The previous prime is 21966883. The next prime is 21966899. The reversal of 21966891 is 19866912.

It is an interprime number because it is at equal distance from previous prime (21966883) and next prime (21966899).

It is a cyclic number.

It is not a de Polignac number, because 21966891 - 2³ = 21966883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21966899) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6325 + ... + 9161.

It is an arithmetic number, because the mean of its divisors is an integer number (1915650).

Almost surely, 2^21966891 is an apocalyptic number.

21966891 is a deficient number, since it is larger than the sum of its proper divisors (8683509).

21966891 is a wasteful number, since it uses less digits than its factorization.

21966891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2958.

The product of its digits is 46656, while the sum is 42.

The square root of 21966891 is about 4686.8849996560. The cubic root of 21966891 is about 280.0632977644.

The spelling of 21966891 in words is "twenty-one million, nine hundred sixty-six thousand, eight hundred ninety-one".