21367890 has 48 divisors (see below), whose sum is σ = 55994328. Its totient is φ = 5653248.

The previous prime is 21367889. The next prime is 21367891. The reversal of 21367890 is 9876312.

It is an interprime number because it is at equal distance from previous prime (21367889) and next prime (21367891).

It can be written as a sum of positive squares in 4 ways, for example, as 17363889 + 4004001 = 4167^2 + 2001^2 .

It is not an unprimeable number, because it can be changed into a prime (21367891) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11464 + ... + 13196.

Almost surely, 2^21367890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21367890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27997164).

21367890 is an abundant number, since it is smaller than the sum of its proper divisors (34626438).

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

21367890 is a wasteful number, since it uses less digits than its factorization.

21367890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1883 (or 1880 counting only the distinct ones).

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

The square root of 21367890 is about 4622.5415087374. The cubic root of 21367890 is about 277.4941805451.

The spelling of 21367890 in words is "twenty-one million, three hundred sixty-seven thousand, eight hundred ninety".