21015774 has 80 divisors (see below), whose sum is σ = 53787888. Its totient is φ = 6075648.

The previous prime is 21015773. The next prime is 21015803. The reversal of 21015774 is 47751012.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21015773) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 35509 + ... + 36095.

Almost surely, 2^21015774 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21015774, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26893944).

21015774 is an abundant number, since it is smaller than the sum of its proper divisors (32772114).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21015774 is a wasteful number, since it uses less digits than its factorization.

21015774 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 631 (or 622 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 21015774 is about 4584.2964563824. The cubic root of 21015774 is about 275.9614785557.

Adding to 21015774 its reverse (47751012), we get a palindrome (68766786).

It can be divided in two parts, 2101 and 5774, that added together give a triangular number (7875 = T₁₂₅).

The spelling of 21015774 in words is "twenty-one million, fifteen thousand, seven hundred seventy-four".