21391392 has 96 divisors (see below), whose sum is σ = 62705664. Its totient is φ = 6329600.

The previous prime is 21391387. The next prime is 21391399. The reversal of 21391392 is 29319312.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is not an unprimeable number, because it can be changed into a prime (21391399) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49417 + ... + 49847.

It is an arithmetic number, because the mean of its divisors is an integer number (653184).

Almost surely, 2^21391392 is an apocalyptic number.

21391392 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21391392, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31352832).

21391392 is an abundant number, since it is smaller than the sum of its proper divisors (41314272).

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

21391392 is a wasteful number, since it uses less digits than its factorization.

21391392 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 502 (or 494 counting only the distinct ones).

The product of its digits is 2916, while the sum is 30.

The square root of 21391392 is about 4625.0829181756. The cubic root of 21391392 is about 277.5958795381.

The spelling of 21391392 in words is "twenty-one million, three hundred ninety-one thousand, three hundred ninety-two".