21351771 has 24 divisors (see below), whose sum is σ = 36002304. Its totient is φ = 11939760.

The previous prime is 21351767. The next prime is 21351773. The reversal of 21351771 is 17715312.

It is a happy number.

It is not a de Polignac number, because 21351771 - 2² = 21351767 is a prime.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21351773) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 645 + ... + 6566.

It is an arithmetic number, because the mean of its divisors is an integer number (1500096).

Almost surely, 2^21351771 is an apocalyptic number.

21351771 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21351771 is a deficient number, since it is larger than the sum of its proper divisors (14650533).

21351771 is a wasteful number, since it uses less digits than its factorization.

21351771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7271 (or 7268 counting only the distinct ones).

The product of its digits is 1470, while the sum is 27.

The square root of 21351771 is about 4620.7976584135. The cubic root of 21351771 is about 277.4243865084.

It can be divided in two parts, 21351 and 771, that added together give a palindrome (22122).

The spelling of 21351771 in words is "twenty-one million, three hundred fifty-one thousand, seven hundred seventy-one".