21291851 has 8 divisors (see below), whose sum is σ = 24570624. Its totient is φ = 18072360.

The previous prime is 21291847. The next prime is 21291883. The reversal of 21291851 is 15819212.

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 21291851 - 2² = 21291847 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21291821) 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, 14045 + ... + 15486.

It is an arithmetic number, because the mean of its divisors is an integer number (3071328).

Almost surely, 2^21291851 is an apocalyptic number.

21291851 is a deficient number, since it is larger than the sum of its proper divisors (3278773).

21291851 is a wasteful number, since it uses less digits than its factorization.

21291851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29641.

The product of its digits is 1440, while the sum is 29.

The square root of 21291851 is about 4614.3093741101. The cubic root of 21291851 is about 277.1646290762.

The spelling of 21291851 in words is "twenty-one million, two hundred ninety-one thousand, eight hundred fifty-one".