21765156 has 48 divisors (see below), whose sum is σ = 58579584. Its totient is φ = 6160896.

The previous prime is 21765119. The next prime is 21765157. The reversal of 21765156 is 65156712.

21765156 = T₃₂₁ + T₃₂₂ + ... + T₅₄₆.

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21765157) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8346 + ... + 10638.

It is an arithmetic number, because the mean of its divisors is an integer number (1220408).

Almost surely, 2^21765156 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21765156, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29289792).

21765156 is an abundant number, since it is smaller than the sum of its proper divisors (36814428).

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

21765156 is a wasteful number, since it uses less digits than its factorization.

21765156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2420 (or 2418 counting only the distinct ones).

The product of its digits is 12600, while the sum is 33.

The square root of 21765156 is about 4665.3141373331. The cubic root of 21765156 is about 279.2033306664.

The spelling of 21765156 in words is "twenty-one million, seven hundred sixty-five thousand, one hundred fifty-six".