21090097 has 4 divisors (see below), whose sum is σ = 24102976. Its totient is φ = 18077220.

The previous prime is 21090073. The next prime is 21090101. The reversal of 21090097 is 79009012.

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 not a de Polignac number, because 21090097 - 2⁷ = 21089969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21090007) 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, 1506429 + ... + 1506442.

It is an arithmetic number, because the mean of its divisors is an integer number (6025744).

Almost surely, 2^21090097 is an apocalyptic number.

It is an amenable number.

21090097 is a deficient number, since it is larger than the sum of its proper divisors (3012879).

21090097 is an equidigital number, since it uses as much as digits as its factorization.

21090097 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3012878.

The product of its (nonzero) digits is 1134, while the sum is 28.

The square root of 21090097 is about 4592.3955622311. The cubic root of 21090097 is about 276.2864115311.

The spelling of 21090097 in words is "twenty-one million, ninety thousand, ninety-seven".