21539011 has 4 divisors (see below), whose sum is σ = 23195872. Its totient is φ = 19882152.

The previous prime is 21539009. The next prime is 21539029. The reversal of 21539011 is 11093512.

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 21539011 - 2¹ = 21539009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21539311) 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, 828411 + ... + 828436.

It is an arithmetic number, because the mean of its divisors is an integer number (5798968).

Almost surely, 2^21539011 is an apocalyptic number.

21539011 is a deficient number, since it is larger than the sum of its proper divisors (1656861).

21539011 is a wasteful number, since it uses less digits than its factorization.

21539011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1656860.

The product of its (nonzero) digits is 270, while the sum is 22.

The square root of 21539011 is about 4641.0140055811. The cubic root of 21539011 is about 278.2329663897.

The spelling of 21539011 in words is "twenty-one million, five hundred thirty-nine thousand, eleven".