21161880 has 96 divisors (see below), whose sum is σ = 71182800. Its totient is φ = 5445888.

The previous prime is 21161869. The next prime is 21161887. The reversal of 21161880 is 8816112.

21161880 = 327² + 328² + ... + 461².

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21161887) 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, 9427 + ... + 11453.

Almost surely, 2^21161880 is an apocalyptic number.

21161880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21161880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35591400).

21161880 is an abundant number, since it is smaller than the sum of its proper divisors (50020920).

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

21161880 is a wasteful number, since it uses less digits than its factorization.

21161880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2073 (or 2066 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 21161880 is about 4600.2043432874. The cubic root of 21161880 is about 276.5995159686.

Adding to 21161880 its reverse (8816112), we get a palindrome (29977992).

The spelling of 21161880 in words is "twenty-one million, one hundred sixty-one thousand, eight hundred eighty".