21530542 has 16 divisors (see below), whose sum is σ = 35441712. Its totient is φ = 9728320.

The previous prime is 21530539. The next prime is 21530543. The reversal of 21530542 is 24503512.

It is a super-3 number, since 3×21530542³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21530543) 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, 978 + ... + 6634.

It is an arithmetic number, because the mean of its divisors is an integer number (2215107).

Almost surely, 2^21530542 is an apocalyptic number.

21530542 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21530542 is a deficient number, since it is larger than the sum of its proper divisors (13911170).

21530542 is a wasteful number, since it uses less digits than its factorization.

21530542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5843.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21530542 is about 4640.1015075104. The cubic root of 21530542 is about 278.1964951408.

The spelling of 21530542 in words is "twenty-one million, five hundred thirty thousand, five hundred forty-two".