21690328 has 32 divisors (see below), whose sum is σ = 45803520. Its totient is φ = 9540000.

The previous prime is 21690293. The next prime is 21690329. The reversal of 21690328 is 82309612.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a self number, because there is not a number n which added to its sum of digits gives 21690328.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690329) 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, 1248 + ... + 6703.

It is an arithmetic number, because the mean of its divisors is an integer number (1431360).

Almost surely, 2^21690328 is an apocalyptic number.

It is an amenable number.

21690328 is an abundant number, since it is smaller than the sum of its proper divisors (24113192).

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

21690328 is a wasteful number, since it uses less digits than its factorization.

21690328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7999 (or 7995 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21690328 is about 4657.2876226405. The cubic root of 21690328 is about 278.8829988639.

The spelling of 21690328 in words is "twenty-one million, six hundred ninety thousand, three hundred twenty-eight".