21390688 has 48 divisors (see below), whose sum is σ = 46678464. Its totient is φ = 9567360.

The previous prime is 21390673. The next prime is 21390727. The reversal of 21390688 is 88609312.

It is a super-2 number, since 2×21390688² = 915123066226688, which contains 22 as substring.

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, 23131 + ... + 24037.

It is an arithmetic number, because the mean of its divisors is an integer number (972468).

Almost surely, 2^21390688 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21390688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23339232).

21390688 is an abundant number, since it is smaller than the sum of its proper divisors (25287776).

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

21390688 is a wasteful number, since it uses less digits than its factorization.

21390688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 995 (or 987 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21390688 is about 4625.0068108058. The cubic root of 21390688 is about 277.5928342377.

The spelling of 21390688 in words is "twenty-one million, three hundred ninety thousand, six hundred eighty-eight".