21151020 has 96 divisors (see below), whose sum is σ = 65640960. Its totient is φ = 5045760.

The previous prime is 21150991. The next prime is 21151027. The reversal of 21151020 is 2015112.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21150987 and 21151005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21151027) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 47961 + ... + 48399.

It is an arithmetic number, because the mean of its divisors is an integer number (683760).

Almost surely, 2^21151020 is an apocalyptic number.

21151020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21151020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32820480).

21151020 is an abundant number, since it is smaller than the sum of its proper divisors (44489940).

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

21151020 is a wasteful number, since it uses less digits than its factorization.

21151020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 535 (or 533 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 12.

The square root of 21151020 is about 4599.0238094622. The cubic root of 21151020 is about 276.5521921212.

Adding to 21151020 its reverse (2015112), we get a palindrome (23166132).

The spelling of 21151020 in words is "twenty-one million, one hundred fifty-one thousand, twenty".