21990105 has 24 divisors (see below), whose sum is σ = 38480832. Its totient is φ = 11615904.

The previous prime is 21990083. The next prime is 21990107. The reversal of 21990105 is 50109912.

It is a happy number.

It is not a de Polignac number, because 21990105 - 2⁶ = 21990041 is a prime.

It is a super-2 number, since 2×21990105² = 967129435822050, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21990107) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2532 + ... + 7098.

It is an arithmetic number, because the mean of its divisors is an integer number (1603368).

Almost surely, 2^21990105 is an apocalyptic number.

It is an amenable number.

21990105 is a deficient number, since it is larger than the sum of its proper divisors (16490727).

21990105 is a wasteful number, since it uses less digits than its factorization.

21990105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4685 (or 4682 counting only the distinct ones).

The product of its (nonzero) digits is 810, while the sum is 27.

The square root of 21990105 is about 4689.3608306463. The cubic root of 21990105 is about 280.1619174034.

The spelling of 21990105 in words is "twenty-one million, nine hundred ninety thousand, one hundred five".