21612539 has 4 divisors (see below), whose sum is σ = 23275056. Its totient is φ = 19950024.

The previous prime is 21612529. The next prime is 21612581. The reversal of 21612539 is 93521612.

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 21612539 - 2¹² = 21608443 is a prime.

It is a super-3 number, since 3×21612539³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21612509) 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, 831239 + ... + 831264.

It is an arithmetic number, because the mean of its divisors is an integer number (5818764).

Almost surely, 2^21612539 is an apocalyptic number.

21612539 is a deficient number, since it is larger than the sum of its proper divisors (1662517).

21612539 is a wasteful number, since it uses less digits than its factorization.

21612539 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1662516.

The product of its digits is 3240, while the sum is 29.

The square root of 21612539 is about 4648.9288013477. The cubic root of 21612539 is about 278.5492092982.

The spelling of 21612539 in words is "twenty-one million, six hundred twelve thousand, five hundred thirty-nine".