21090369 has 4 divisors (see below), whose sum is σ = 28120496. Its totient is φ = 14060244.

The previous prime is 21090367. The next prime is 21090371. The reversal of 21090369 is 96309012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (21090367) and next prime (21090371).

It is not a de Polignac number, because 21090369 - 2¹ = 21090367 is a prime.

It is a super-2 number, since 2×21090369² = 889607329112322, which contains 22 as substring.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21090367) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3515059 + ... + 3515064.

It is an arithmetic number, because the mean of its divisors is an integer number (7030124).

Almost surely, 2^21090369 is an apocalyptic number.

It is an amenable number.

21090369 is a deficient number, since it is larger than the sum of its proper divisors (7030127).

21090369 is an equidigital number, since it uses as much as digits as its factorization.

21090369 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7030126.

The product of its (nonzero) digits is 2916, while the sum is 30.

The square root of 21090369 is about 4592.4251763094. The cubic root of 21090369 is about 276.2875992857.

The spelling of 21090369 in words is "twenty-one million, ninety thousand, three hundred sixty-nine".