21292720 has 20 divisors (see below), whose sum is σ = 49505760. Its totient is φ = 8517056.

The previous prime is 21292717. The next prime is 21292729. The reversal of 21292720 is 2729212.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (21292729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133000 + ... + 133159.

It is an arithmetic number, because the mean of its divisors is an integer number (2475288).

Almost surely, 2^21292720 is an apocalyptic number.

21292720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21292720 is an abundant number, since it is smaller than the sum of its proper divisors (28213040).

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

21292720 is a wasteful number, since it uses less digits than its factorization.

21292720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266172 (or 266166 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21292720 is about 4614.4035367532. The cubic root of 21292720 is about 277.1683997330.

The spelling of 21292720 in words is "twenty-one million, two hundred ninety-two thousand, seven hundred twenty".