21206742 has 32 divisors (see below), whose sum is σ = 43338240. Its totient is φ = 6916800.

The previous prime is 21206699. The next prime is 21206747. The reversal of 21206742 is 24760212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206747) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 80503 + ... + 80765.

It is an arithmetic number, because the mean of its divisors is an integer number (1354320).

Almost surely, 2^21206742 is an apocalyptic number.

21206742 is an abundant number, since it is smaller than the sum of its proper divisors (22131498).

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

21206742 is a wasteful number, since it uses less digits than its factorization.

21206742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 508.

The product of its (nonzero) digits is 1344, while the sum is 24.

The square root of 21206742 is about 4605.0778495048. The cubic root of 21206742 is about 276.7948365031.

Adding to 21206742 its reverse (24760212), we get a palindrome (45966954).

The spelling of 21206742 in words is "twenty-one million, two hundred six thousand, seven hundred forty-two".