21156930 has 64 divisors (see below), whose sum is σ = 56954880. Its totient is φ = 5588352.

The previous prime is 21156929. The next prime is 21156931. The reversal of 21156930 is 3965112.

It is an interprime number because it is at equal distance from previous prime (21156929) and next prime (21156931).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21156894 and 21156903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21156931) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 33982 + ... + 34598.

It is an arithmetic number, because the mean of its divisors is an integer number (889920).

Almost surely, 2^21156930 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21156930, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28477440).

21156930 is an abundant number, since it is smaller than the sum of its proper divisors (35797950).

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

21156930 is a wasteful number, since it uses less digits than its factorization.

21156930 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 760 (or 754 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 21156930 is about 4599.6662922434. Note that the first 3 decimals coincide. The cubic root of 21156930 is about 276.5779477151.

It can be divided in two parts, 2115 and 6930, that added together give a triangular number (9045 = T₁₃₄).

The spelling of 21156930 in words is "twenty-one million, one hundred fifty-six thousand, nine hundred thirty".