21007320 has 32 divisors (see below), whose sum is σ = 63022320. Its totient is φ = 5601920.

The previous prime is 21007319. The next prime is 21007321. The reversal of 21007320 is 2370012.

It is an interprime number because it is at equal distance from previous prime (21007319) and next prime (21007321).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21007320.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21007321) 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, 87411 + ... + 87650.

Almost surely, 2^21007320 is an apocalyptic number.

21007320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21007320 is an abundant number, since it is smaller than the sum of its proper divisors (42015000).

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

21007320 is a wasteful number, since it uses less digits than its factorization.

21007320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 175075 (or 175071 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 15.

The square root of 21007320 is about 4583.3743028472. The cubic root of 21007320 is about 275.9244699856.

Adding to 21007320 its reverse (2370012), we get a palindrome (23377332).

The spelling of 21007320 in words is "twenty-one million, seven thousand, three hundred twenty".