21378516 has 12 divisors (see below), whose sum is σ = 49883232. Its totient is φ = 7126168.

The previous prime is 21378491. The next prime is 21378521. The reversal of 21378516 is 61587312.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 890760 + ... + 890783.

It is an arithmetic number, because the mean of its divisors is an integer number (4156936).

Almost surely, 2^21378516 is an apocalyptic number.

It is an amenable number.

21378516 is an abundant number, since it is smaller than the sum of its proper divisors (28504716).

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

21378516 is a wasteful number, since it uses less digits than its factorization.

21378516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1781550 (or 1781548 counting only the distinct ones).

The product of its digits is 10080, while the sum is 33.

The square root of 21378516 is about 4623.6907336023. The cubic root of 21378516 is about 277.5401711182.

The spelling of 21378516 in words is "twenty-one million, three hundred seventy-eight thousand, five hundred sixteen".