21305740 has 24 divisors (see below), whose sum is σ = 44829792. Its totient is φ = 8505600.

The previous prime is 21305737. The next prime is 21305741. The reversal of 21305740 is 4750312.

It is not an unprimeable number, because it can be changed into a prime (21305741) 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, 17140 + ... + 18340.

It is an arithmetic number, because the mean of its divisors is an integer number (1867908).

Almost surely, 2^21305740 is an apocalyptic number.

21305740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21305740 is an abundant number, since it is smaller than the sum of its proper divisors (23524052).

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

21305740 is a wasteful number, since it uses less digits than its factorization.

21305740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2097 (or 2095 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 22.

The square root of 21305740 is about 4615.8141210408. The cubic root of 21305740 is about 277.2248822187.

The spelling of 21305740 in words is "twenty-one million, three hundred five thousand, seven hundred forty".