21423740 has 96 divisors (see below), whose sum is σ = 53089344. Its totient is φ = 7188480.

The previous prime is 21423709. The next prime is 21423751. The reversal of 21423740 is 4732412.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 163475 + ... + 163605.

It is an arithmetic number, because the mean of its divisors is an integer number (553014).

Almost surely, 2^21423740 is an apocalyptic number.

21423740 is a gapful number since it is divisible by the number (20) 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 21423740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26544672).

21423740 is an abundant number, since it is smaller than the sum of its proper divisors (31665604).

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

21423740 is a wasteful number, since it uses less digits than its factorization.

21423740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 207 (or 205 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21423740 is about 4628.5786155147. The cubic root of 21423740 is about 277.7357356224.

The spelling of 21423740 in words is "twenty-one million, four hundred twenty-three thousand, seven hundred forty".