21489780 has 48 divisors (see below), whose sum is σ = 64802304. Its totient is φ = 5289600.

The previous prime is 21489761. The next prime is 21489791. The reversal of 21489780 is 8798412.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12996 + ... + 14555.

It is an arithmetic number, because the mean of its divisors is an integer number (1350048).

Almost surely, 2^21489780 is an apocalyptic number.

21489780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21489780 is an abundant number, since it is smaller than the sum of its proper divisors (43312524).

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

21489780 is a wasteful number, since it uses less digits than its factorization.

21489780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27576 (or 27574 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 21489780 is about 4635.7070658099. The cubic root of 21489780 is about 278.0208220693.

It can be divided in two parts, 21 and 489780, that multiplied together give a triangular number (10285380 = T₄₅₃₅).

The spelling of 21489780 in words is "twenty-one million, four hundred eighty-nine thousand, seven hundred eighty".