21090549 has 8 divisors (see below), whose sum is σ = 28459872. Its totient is φ = 13890800.

The previous prime is 21090547. The next prime is 21090583. The reversal of 21090549 is 94509012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21090549 - 2¹ = 21090547 is a prime.

It is a super-2 number, since 2×21090549² = 889622514242802, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090547) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 42102 + ... + 42599.

It is an arithmetic number, because the mean of its divisors is an integer number (3557484).

Almost surely, 2^21090549 is an apocalyptic number.

It is an amenable number.

21090549 is a deficient number, since it is larger than the sum of its proper divisors (7369323).

21090549 is an equidigital number, since it uses as much as digits as its factorization.

21090549 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84787.

The product of its (nonzero) digits is 3240, while the sum is 30.

The square root of 21090549 is about 4592.4447737561. Note that the first 3 decimals coincide. The cubic root of 21090549 is about 276.2883852942.

The spelling of 21090549 in words is "twenty-one million, ninety thousand, five hundred forty-nine".