21247542 has 16 divisors (see below), whose sum is σ = 47216880. Its totient is φ = 7082496.

The previous prime is 21247537. The next prime is 21247543. The reversal of 21247542 is 24574212.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21247543) 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 7 ways as a sum of consecutive naturals, for example, 196683 + ... + 196790.

It is an arithmetic number, because the mean of its divisors is an integer number (2951055).

Almost surely, 2^21247542 is an apocalyptic number.

21247542 is an abundant number, since it is smaller than the sum of its proper divisors (25969338).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21247542 is a wasteful number, since it uses less digits than its factorization.

21247542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 393484 (or 393478 counting only the distinct ones).

The product of its digits is 4480, while the sum is 27.

The square root of 21247542 is about 4609.5056134037. The cubic root of 21247542 is about 276.9722328338.

The spelling of 21247542 in words is "twenty-one million, two hundred forty-seven thousand, five hundred forty-two".