21355730 has 48 divisors (see below), whose sum is σ = 43956864. Its totient is φ = 7407840.

The previous prime is 21355729. The next prime is 21355769. The reversal of 21355730 is 3755312.

It is a self number, because there is not a number n which added to its sum of digits gives 21355730.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 58007 + ... + 58373.

It is an arithmetic number, because the mean of its divisors is an integer number (915768).

Almost surely, 2^21355730 is an apocalyptic number.

21355730 is an abundant number, since it is smaller than the sum of its proper divisors (22601134).

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

21355730 is a wasteful number, since it uses less digits than its factorization.

21355730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 431 (or 408 counting only the distinct ones).

The product of its (nonzero) digits is 3150, while the sum is 26.

The square root of 21355730 is about 4621.2260277983. The cubic root of 21355730 is about 277.4415319288.

The spelling of 21355730 in words is "twenty-one million, three hundred fifty-five thousand, seven hundred thirty".