21539967 has 8 divisors (see below), whose sum is σ = 29004720. Its totient is φ = 14217600.

The previous prime is 21539933. The next prime is 21539971. The reversal of 21539967 is 76993512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21539967 - 2⁷ = 21539839 is a prime.

It is a super-2 number, since 2×21539967² = 927940356722178, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21539267) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35242 + ... + 35847.

It is an arithmetic number, because the mean of its divisors is an integer number (3625590).

Almost surely, 2^21539967 is an apocalyptic number.

21539967 is a deficient number, since it is larger than the sum of its proper divisors (7464753).

21539967 is a wasteful number, since it uses less digits than its factorization.

21539967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71193.

The product of its digits is 102060, while the sum is 42.

The square root of 21539967 is about 4641.1169991716. The cubic root of 21539967 is about 278.2370827468.

The spelling of 21539967 in words is "twenty-one million, five hundred thirty-nine thousand, nine hundred sixty-seven".