21051491 has 8 divisors (see below), whose sum is σ = 22834224. Its totient is φ = 19329280.

The previous prime is 21051479. The next prime is 21051493. The reversal of 21051491 is 19415012.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21051491 - 2⁶ = 21051427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21051493) 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, 14405 + ... + 15798.

It is an arithmetic number, because the mean of its divisors is an integer number (2854278).

Almost surely, 2^21051491 is an apocalyptic number.

21051491 is a deficient number, since it is larger than the sum of its proper divisors (1782733).

21051491 is a wasteful number, since it uses less digits than its factorization.

21051491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30261.

The product of its (nonzero) digits is 360, while the sum is 23.

The square root of 21051491 is about 4588.1903840185. The cubic root of 21051491 is about 276.1177252806.

The spelling of 21051491 in words is "twenty-one million, fifty-one thousand, four hundred ninety-one".