16921890 has 24 divisors (see below), whose sum is σ = 43997148. Its totient is φ = 4512480.

The previous prime is 16921867. The next prime is 16921901. The reversal of 16921890 is 9812961.

It can be written as a sum of positive squares in 2 ways, for example, as 16670889 + 251001 = 4083^2 + 501^2 .

It is a super-2 number, since 2×16921890² = 572700722344200, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 93921 + ... + 94100.

Almost surely, 2^16921890 is an apocalyptic number.

16921890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

16921890 is an abundant number, since it is smaller than the sum of its proper divisors (27075258).

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

16921890 is a wasteful number, since it uses less digits than its factorization.

16921890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188034 (or 188031 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 16921890 is about 4113.6224911871. The cubic root of 16921890 is about 256.7337449537.

The spelling of 16921890 in words is "sixteen million, nine hundred twenty-one thousand, eight hundred ninety".