21728990 has 16 divisors (see below), whose sum is σ = 40169952. Its totient is φ = 8456544.

The previous prime is 21728981. The next prime is 21729007. The reversal of 21728990 is 9982712.

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, 28994 + ... + 29733.

It is an arithmetic number, because the mean of its divisors is an integer number (2510622).

Almost surely, 2^21728990 is an apocalyptic number.

21728990 is a deficient number, since it is larger than the sum of its proper divisors (18440962).

21728990 is a wasteful number, since it uses less digits than its factorization.

21728990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58771.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 21728990 is about 4661.4364738780. The cubic root of 21728990 is about 279.0485991658.

The spelling of 21728990 in words is "twenty-one million, seven hundred twenty-eight thousand, nine hundred ninety".