21929391 has 12 divisors (see below), whose sum is σ = 34555560. Its totient is φ = 13290480.

The previous prime is 21929389. The next prime is 21929393. The reversal of 21929391 is 19392912.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21929389) and next prime (21929393).

It is not a de Polignac number, because 21929391 - 2¹ = 21929389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21929393) 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, 110656 + ... + 110853.

It is an arithmetic number, because the mean of its divisors is an integer number (2879630).

Almost surely, 2^21929391 is an apocalyptic number.

21929391 is a deficient number, since it is larger than the sum of its proper divisors (12626169).

21929391 is a wasteful number, since it uses less digits than its factorization.

21929391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221526 (or 221523 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 21929391 is about 4682.8827659893. The cubic root of 21929391 is about 279.9038402792.

The spelling of 21929391 in words is "twenty-one million, nine hundred twenty-nine thousand, three hundred ninety-one".