21091930 has 32 divisors (see below), whose sum is σ = 39207168. Its totient is φ = 8164800.

The previous prime is 21091913. The next prime is 21091937. The reversal of 21091930 is 3919012.

It is a super-2 number, since 2×21091930² = 889739022249800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21091895 and 21091904.

It is not an unprimeable number, because it can be changed into a prime (21091937) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 77695 + ... + 77965.

It is an arithmetic number, because the mean of its divisors is an integer number (1225224).

Almost surely, 2^21091930 is an apocalyptic number.

21091930 is a deficient number, since it is larger than the sum of its proper divisors (18115238).

21091930 is a wasteful number, since it uses less digits than its factorization.

21091930 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 502.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 21091930 is about 4592.5951269408. The cubic root of 21091930 is about 276.2944155771.

The spelling of 21091930 in words is "twenty-one million, ninety-one thousand, nine hundred thirty".