21072390 has 16 divisors (see below), whose sum is σ = 50573808. Its totient is φ = 5619296.

The previous prime is 21072379. The next prime is 21072407. The reversal of 21072390 is 9327012.

It is a self number, because there is not a number n which added to its sum of digits gives 21072390.

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, 351177 + ... + 351236.

It is an arithmetic number, because the mean of its divisors is an integer number (3160863).

Almost surely, 2^21072390 is an apocalyptic number.

21072390 is an abundant number, since it is smaller than the sum of its proper divisors (29501418).

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

21072390 is a wasteful number, since it uses less digits than its factorization.

21072390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 702423.

The product of its (nonzero) digits is 756, while the sum is 24.

The square root of 21072390 is about 4590.4672964743. The cubic root of 21072390 is about 276.2090675961.

The spelling of 21072390 in words is "twenty-one million, seventy-two thousand, three hundred ninety".