21670691 has 12 divisors (see below), whose sum is σ = 25567920. Its totient is φ = 18310320.

The previous prime is 21670679. The next prime is 21670703. The reversal of 21670691 is 19607612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21670679) and next prime (21670703).

It is not a de Polignac number, because 21670691 - 2¹⁰ = 21669667 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21670601) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 365 + ... + 6593.

It is an arithmetic number, because the mean of its divisors is an integer number (2130660).

Almost surely, 2^21670691 is an apocalyptic number.

21670691 is a deficient number, since it is larger than the sum of its proper divisors (3897229).

21670691 is an equidigital number, since it uses as much as digits as its factorization.

21670691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6314 (or 6307 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 21670691 is about 4655.1789439290. The cubic root of 21670691 is about 278.7988126627.

It can be divided in two parts, 216 and 70691, that added together give a palindrome (70907).

The spelling of 21670691 in words is "twenty-one million, six hundred seventy thousand, six hundred ninety-one".