21863890 has 8 divisors (see below), whose sum is σ = 39355020. Its totient is φ = 8745552.

The previous prime is 21863879. The next prime is 21863893. The reversal of 21863890 is 9836812.

It can be written as a sum of positive squares in 2 ways, for example, as 21706281 + 157609 = 4659^2 + 397^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21863893) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1093185 + ... + 1093204.

Almost surely, 2^21863890 is an apocalyptic number.

21863890 is a deficient number, since it is larger than the sum of its proper divisors (17491130).

21863890 is a wasteful number, since it uses less digits than its factorization.

21863890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2186396.

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

The square root of 21863890 is about 4675.8838736650. The cubic root of 21863890 is about 279.6248803247.

The spelling of 21863890 in words is "twenty-one million, eight hundred sixty-three thousand, eight hundred ninety".