21181967 has 4 divisors (see below), whose sum is σ = 21195120. Its totient is φ = 21168816.

The previous prime is 21181961. The next prime is 21181997. The reversal of 21181967 is 76918112.

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

It is a cyclic number.

It is not a de Polignac number, because 21181967 - 2¹⁴ = 21165583 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21181961) 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, 3758 + ... + 7515.

It is an arithmetic number, because the mean of its divisors is an integer number (5298780).

Almost surely, 2^21181967 is an apocalyptic number.

21181967 is the 3758-th pentagonal number.

21181967 is a deficient number, since it is larger than the sum of its proper divisors (13153).

21181967 is a wasteful number, since it uses less digits than its factorization.

21181967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13152.

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

The square root of 21181967 is about 4602.3870980177. The cubic root of 21181967 is about 276.6870050047.

The spelling of 21181967 in words is "twenty-one million, one hundred eighty-one thousand, nine hundred sixty-seven".