21290691 has 4 divisors (see below), whose sum is σ = 28387592. Its totient is φ = 14193792.

The previous prime is 21290653. The next prime is 21290693. The reversal of 21290691 is 19609212.

It is a happy number.

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

It is not a de Polignac number, because 21290691 - 2¹⁴ = 21274307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21290693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3548446 + ... + 3548451.

It is an arithmetic number, because the mean of its divisors is an integer number (7096898).

Almost surely, 2^21290691 is an apocalyptic number.

21290691 is a deficient number, since it is larger than the sum of its proper divisors (7096901).

21290691 is an equidigital number, since it uses as much as digits as its factorization.

21290691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7096900.

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 21290691 is about 4614.1836764481. The cubic root of 21290691 is about 277.1595955885.

The spelling of 21290691 in words is "twenty-one million, two hundred ninety thousand, six hundred ninety-one".