21856730 has 32 divisors (see below), whose sum is σ = 47609856. Its totient is φ = 7052544.

The previous prime is 21856697. The next prime is 21856733. The reversal of 21856730 is 3765812.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21856733) 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, 7994 + ... + 10373.

It is an arithmetic number, because the mean of its divisors is an integer number (1487808).

Almost surely, 2^21856730 is an apocalyptic number.

21856730 is an abundant number, since it is smaller than the sum of its proper divisors (25753126).

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

21856730 is a wasteful number, since it uses less digits than its factorization.

21856730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18398.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 21856730 is about 4675.1181803244. The cubic root of 21856730 is about 279.5943530835.

The spelling of 21856730 in words is "twenty-one million, eight hundred fifty-six thousand, seven hundred thirty".