21209880 has 128 divisors (see below), whose sum is σ = 69439680. Its totient is φ = 5160960.

The previous prime is 21209873. The next prime is 21209927. The reversal of 21209880 is 8890212.

It is a super-2 number, since 2×21209880² = 899718019228800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 75340 + ... + 75620.

Almost surely, 2^21209880 is an apocalyptic number.

21209880 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 21209880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34719840).

21209880 is an abundant number, since it is smaller than the sum of its proper divisors (48229800).

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

21209880 is a wasteful number, since it uses less digits than its factorization.

21209880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 349 (or 345 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 30.

The square root of 21209880 is about 4605.4185477544. The cubic root of 21209880 is about 276.8084884407.

The spelling of 21209880 in words is "twenty-one million, two hundred nine thousand, eight hundred eighty".