21191090 has 16 divisors (see below), whose sum is σ = 38235672. Its totient is φ = 8456064.

The previous prime is 21191081. The next prime is 21191111. The reversal of 21191090 is 9019112.

It can be written as a sum of positive squares in 4 ways, for example, as 18139081 + 3052009 = 4259^2 + 1747^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2252 + ... + 6888.

Almost surely, 2^21191090 is an apocalyptic number.

21191090 is a deficient number, since it is larger than the sum of its proper divisors (17044582).

21191090 is a wasteful number, since it uses less digits than its factorization.

21191090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5101.

The product of its (nonzero) digits is 162, while the sum is 23.

The square root of 21191090 is about 4603.3781074337. The cubic root of 21191090 is about 276.7267220157.

The spelling of 21191090 in words is "twenty-one million, one hundred ninety-one thousand, ninety".