21128742 has 16 divisors (see below), whose sum is σ = 46952880. Its totient is φ = 7042896.

The previous prime is 21128719. The next prime is 21128747. The reversal of 21128742 is 24782112.

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 (21128747) 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, 195583 + ... + 195690.

It is an arithmetic number, because the mean of its divisors is an integer number (2934555).

Almost surely, 2^21128742 is an apocalyptic number.

21128742 is an abundant number, since it is smaller than the sum of its proper divisors (25824138).

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

21128742 is a wasteful number, since it uses less digits than its factorization.

21128742 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 391284 (or 391278 counting only the distinct ones).

The product of its digits is 1792, while the sum is 27.

The square root of 21128742 is about 4596.6011356218. The cubic root of 21128742 is about 276.4550621466.

The spelling of 21128742 in words is "twenty-one million, one hundred twenty-eight thousand, seven hundred forty-two".