21799491 has 32 divisors (see below), whose sum is σ = 35458560. Its totient is φ = 11629056.

The previous prime is 21799487. The next prime is 21799499. The reversal of 21799491 is 19499712.

It is not a de Polignac number, because 21799491 - 2² = 21799487 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21799499) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 80905 + ... + 81173.

It is an arithmetic number, because the mean of its divisors is an integer number (1108080).

Almost surely, 2^21799491 is an apocalyptic number.

21799491 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21799491 is a deficient number, since it is larger than the sum of its proper divisors (13659069).

21799491 is a wasteful number, since it uses less digits than its factorization.

21799491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 523.

The product of its digits is 40824, while the sum is 42.

The square root of 21799491 is about 4668.9925037421. The cubic root of 21799491 is about 279.3500699444.

The spelling of 21799491 in words is "twenty-one million, seven hundred ninety-nine thousand, four hundred ninety-one".