21967421 has 16 divisors (see below), whose sum is σ = 25643520. Its totient is φ = 18431280.

The previous prime is 21967409. The next prime is 21967433. The reversal of 21967421 is 12476912.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21967409) and next prime (21967433).

It is not a de Polignac number, because 21967421 - 2²² = 17773117 is a prime.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21967441) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 104006 + ... + 104216.

It is an arithmetic number, because the mean of its divisors is an integer number (1602720).

Almost surely, 2^21967421 is an apocalyptic number.

It is an amenable number.

21967421 is a deficient number, since it is larger than the sum of its proper divisors (3676099).

21967421 is a wasteful number, since it uses less digits than its factorization.

21967421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 464.

The product of its digits is 6048, while the sum is 32.

The square root of 21967421 is about 4686.9415400664. The cubic root of 21967421 is about 280.0655501292.

The spelling of 21967421 in words is "twenty-one million, nine hundred sixty-seven thousand, four hundred twenty-one".