21418390 has 24 divisors (see below), whose sum is σ = 44848512. Its totient is φ = 7343280.

The previous prime is 21418379. The next prime is 21418403. The reversal of 21418390 is 9381412.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 21366 + ... + 22345.

It is an arithmetic number, because the mean of its divisors is an integer number (1868688).

Almost surely, 2^21418390 is an apocalyptic number.

21418390 is an abundant number, since it is smaller than the sum of its proper divisors (23430122).

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

21418390 is a wasteful number, since it uses less digits than its factorization.

21418390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43732 (or 43725 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21418390 is about 4628.0006482281. Note that the first 3 decimals coincide. The cubic root of 21418390 is about 277.7126147000.

The spelling of 21418390 in words is "twenty-one million, four hundred eighteen thousand, three hundred ninety".