21571890 has 16 divisors (see below), whose sum is σ = 51772608. Its totient is φ = 5752496.

The previous prime is 21571867. The next prime is 21571903. The reversal of 21571890 is 9817512.

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, 359502 + ... + 359561.

It is an arithmetic number, because the mean of its divisors is an integer number (3235788).

Almost surely, 2^21571890 is an apocalyptic number.

21571890 is an abundant number, since it is smaller than the sum of its proper divisors (30200718).

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

21571890 is a wasteful number, since it uses less digits than its factorization.

21571890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 719073.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21571890 is about 4644.5548764117. The cubic root of 21571890 is about 278.3744673291.

The spelling of 21571890 in words is "twenty-one million, five hundred seventy-one thousand, eight hundred ninety".