21763890 has 80 divisors (see below), whose sum is σ = 59337432. Its totient is φ = 5723136.

The previous prime is 21763883. The next prime is 21763897. The reversal of 21763890 is 9836712.

21763890 is a `hidden beast` number, since 2 + 17 + 638 + 9 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (21763883) and next prime (21763897).

It can be written as a sum of positive squares in 4 ways, for example, as 13417569 + 8346321 = 3663^2 + 2889^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21763897) 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 39 ways as a sum of consecutive naturals, for example, 78432 + ... + 78708.

Almost surely, 2^21763890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21763890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29668716).

21763890 is an abundant number, since it is smaller than the sum of its proper divisors (37573542).

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

21763890 is a wasteful number, since it uses less digits than its factorization.

21763890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 393 (or 384 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21763890 is about 4665.1784531784. The cubic root of 21763890 is about 279.1979171472.

The spelling of 21763890 in words is "twenty-one million, seven hundred sixty-three thousand, eight hundred ninety".