21870320 has 40 divisors (see below), whose sum is σ = 51184224. Its totient is φ = 8690432.

The previous prime is 21870307. The next prime is 21870323. The reversal of 21870320 is 2307812.

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21870323) 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, 12542 + ... + 14178.

Almost surely, 2^21870320 is an apocalyptic number.

21870320 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 21870320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25592112).

21870320 is an abundant number, since it is smaller than the sum of its proper divisors (29313904).

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

21870320 is a wasteful number, since it uses less digits than its factorization.

21870320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1817 (or 1811 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21870320 is about 4676.5713936601. The cubic root of 21870320 is about 279.6522894721.

The spelling of 21870320 in words is "twenty-one million, eight hundred seventy thousand, three hundred twenty".