21919491 has 40 divisors (see below), whose sum is σ = 36317424. Its totient is φ = 13063680.

The previous prime is 21919487. The next prime is 21919501. The reversal of 21919491 is 19491912.

It is not a de Polignac number, because 21919491 - 2² = 21919487 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21919411) 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 39 ways as a sum of consecutive naturals, for example, 64875 + ... + 65211.

Almost surely, 2^21919491 is an apocalyptic number.

21919491 is a deficient number, since it is larger than the sum of its proper divisors (14397933).

21919491 is a wasteful number, since it uses less digits than its factorization.

21919491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433 (or 424 counting only the distinct ones).

The product of its digits is 5832, while the sum is 36.

The square root of 21919491 is about 4681.8256054663. The cubic root of 21919491 is about 279.8617131765.

The spelling of 21919491 in words is "twenty-one million, nine hundred nineteen thousand, four hundred ninety-one".