21549667 has 4 divisors (see below), whose sum is σ = 22683880. Its totient is φ = 20415456.

The previous prime is 21549637. The next prime is 21549677. The reversal of 21549667 is 76694512.

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 21549667 - 2²³ = 13161059 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21549637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 567078 + ... + 567115.

It is an arithmetic number, because the mean of its divisors is an integer number (5670970).

Almost surely, 2^21549667 is an apocalyptic number.

21549667 is a deficient number, since it is larger than the sum of its proper divisors (1134213).

21549667 is a wasteful number, since it uses less digits than its factorization.

21549667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1134212.

The product of its digits is 90720, while the sum is 40.

The square root of 21549667 is about 4642.1618886032. The cubic root of 21549667 is about 278.2788422456.

The spelling of 21549667 in words is "twenty-one million, five hundred forty-nine thousand, six hundred sixty-seven".