21391242 has 16 divisors (see below), whose sum is σ = 44642880. Its totient is φ = 6820352.

The previous prime is 21391213. The next prime is 21391259. The reversal of 21391242 is 24219312.

It is a plaindrome in base 16.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77367 + ... + 77642.

It is an arithmetic number, because the mean of its divisors is an integer number (2790180).

Almost surely, 2^21391242 is an apocalyptic number.

21391242 is an abundant number, since it is smaller than the sum of its proper divisors (23251638).

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

21391242 is a wasteful number, since it uses less digits than its factorization.

21391242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155037.

The product of its digits is 864, while the sum is 24.

The square root of 21391242 is about 4625.0667022217. The cubic root of 21391242 is about 277.5952306871.

The spelling of 21391242 in words is "twenty-one million, three hundred ninety-one thousand, two hundred forty-two".