21475691 has 4 divisors (see below), whose sum is σ = 21559512. Its totient is φ = 21391872.

The previous prime is 21475687. The next prime is 21475697. The reversal of 21475691 is 19657412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21475691 - 2² = 21475687 is a prime.

It is a super-2 number, since 2×21475691² = 922410607854962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21475697) 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, 41525 + ... + 42038.

It is an arithmetic number, because the mean of its divisors is an integer number (5389878).

Almost surely, 2^21475691 is an apocalyptic number.

21475691 is a deficient number, since it is larger than the sum of its proper divisors (83821).

21475691 is an equidigital number, since it uses as much as digits as its factorization.

21475691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83820.

The product of its digits is 15120, while the sum is 35.

The square root of 21475691 is about 4634.1871994990. The cubic root of 21475691 is about 277.9600506748.

The spelling of 21475691 in words is "twenty-one million, four hundred seventy-five thousand, six hundred ninety-one".