21679890 has 16 divisors (see below), whose sum is σ = 52031808. Its totient is φ = 5781296.

The previous prime is 21679871. The next prime is 21679897. The reversal of 21679890 is 9897612.

It is not an unprimeable number, because it can be changed into a prime (21679897) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 361302 + ... + 361361.

It is an arithmetic number, because the mean of its divisors is an integer number (3251988).

Almost surely, 2^21679890 is an apocalyptic number.

21679890 is an abundant number, since it is smaller than the sum of its proper divisors (30351918).

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

21679890 is a wasteful number, since it uses less digits than its factorization.

21679890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 722673.

The product of its (nonzero) digits is 54432, while the sum is 42.

The square root of 21679890 is about 4656.1668784527. The cubic root of 21679890 is about 278.8382562207.

The spelling of 21679890 in words is "twenty-one million, six hundred seventy-nine thousand, eight hundred ninety".