21021156 has 36 divisors (see below), whose sum is σ = 57225532. Its totient is φ = 6467904.

The previous prime is 21021127. The next prime is 21021157. The reversal of 21021156 is 65112012.

It can be written as a sum of positive squares in 2 ways, for example, as 2822400 + 18198756 = 1680^2 + 4266^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21021157) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 21991 + ... + 22926.

Almost surely, 2^21021156 is an apocalyptic number.

21021156 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21021156 is an abundant number, since it is smaller than the sum of its proper divisors (36204376).

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

21021156 is a wasteful number, since it uses less digits than its factorization.

21021156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44940 (or 44935 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21021156 is about 4584.8834227273. The cubic root of 21021156 is about 275.9850338451.

Adding to 21021156 its reverse (65112012), we get a palindrome (86133168).

The spelling of 21021156 in words is "twenty-one million, twenty-one thousand, one hundred fifty-six".