21145780 has 24 divisors (see below), whose sum is σ = 44497152. Its totient is φ = 8440992.

The previous prime is 21145771. The next prime is 21145799. The reversal of 21145780 is 8754112.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14149 + ... + 15571.

It is an arithmetic number, because the mean of its divisors is an integer number (1854048).

Almost surely, 2^21145780 is an apocalyptic number.

21145780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21145780 is an abundant number, since it is smaller than the sum of its proper divisors (23351372).

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

21145780 is a wasteful number, since it uses less digits than its factorization.

21145780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2175 (or 2173 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 21145780 is about 4598.4540880605. The cubic root of 21145780 is about 276.5293523531.

Adding to 21145780 its reverse (8754112), we get a palindrome (29899892).

The spelling of 21145780 in words is "twenty-one million, one hundred forty-five thousand, seven hundred eighty".