21731620 has 24 divisors (see below), whose sum is σ = 47109888. Its totient is φ = 8412000.

The previous prime is 21731597. The next prime is 21731621. The reversal of 21731620 is 2613712.

It is a junction number, because it is equal to n+sod(n) for n = 21731591 and 21731600.

It is not an unprimeable number, because it can be changed into a prime (21731621) 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 7 ways as a sum of consecutive naturals, for example, 16906 + ... + 18145.

It is an arithmetic number, because the mean of its divisors is an integer number (1962912).

Almost surely, 2^21731620 is an apocalyptic number.

21731620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21731620 is an abundant number, since it is smaller than the sum of its proper divisors (25378268).

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

21731620 is a wasteful number, since it uses less digits than its factorization.

21731620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35091 (or 35089 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21731620 is about 4661.7185672239. The cubic root of 21731620 is about 279.0598570630.

The spelling of 21731620 in words is "twenty-one million, seven hundred thirty-one thousand, six hundred twenty".