21709491 has 8 divisors (see below), whose sum is σ = 29728464. Its totient is φ = 14081760.

The previous prime is 21709477. The next prime is 21709511. The reversal of 21709491 is 19490712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21709491 - 2⁹ = 21708979 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21709411) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 97680 + ... + 97901.

It is an arithmetic number, because the mean of its divisors is an integer number (3716058).

Almost surely, 2^21709491 is an apocalyptic number.

21709491 is a deficient number, since it is larger than the sum of its proper divisors (8018973).

21709491 is a wasteful number, since it uses less digits than its factorization.

21709491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195621.

The product of its (nonzero) digits is 4536, while the sum is 33.

The square root of 21709491 is about 4659.3444817914. The cubic root of 21709491 is about 278.9651039975.

The spelling of 21709491 in words is "twenty-one million, seven hundred nine thousand, four hundred ninety-one".