21751890 has 32 divisors (see below), whose sum is σ = 52327296. Its totient is φ = 5786880.

The previous prime is 21751843. The next prime is 21751913. The reversal of 21751890 is 9815712.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24250 + ... + 25130.

It is an arithmetic number, because the mean of its divisors is an integer number (1635228).

Almost surely, 2^21751890 is an apocalyptic number.

21751890 is an abundant number, since it is smaller than the sum of its proper divisors (30575406).

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

21751890 is a wasteful number, since it uses less digits than its factorization.

21751890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1714.

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

The square root of 21751890 is about 4663.8921514117. The cubic root of 21751890 is about 279.1465937400.

The spelling of 21751890 in words is "twenty-one million, seven hundred fifty-one thousand, eight hundred ninety".