21019770 has 64 divisors (see below), whose sum is σ = 56586240. Its totient is φ = 5552064.

The previous prime is 21019729. The next prime is 21019771. The reversal of 21019770 is 7791012.

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21019771) 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, 33984 + ... + 34596.

It is an arithmetic number, because the mean of its divisors is an integer number (884160).

Almost surely, 2^21019770 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21019770, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28293120).

21019770 is an abundant number, since it is smaller than the sum of its proper divisors (35566470).

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

21019770 is a wasteful number, since it uses less digits than its factorization.

21019770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 756 (or 750 counting only the distinct ones).

The product of its (nonzero) digits is 882, while the sum is 27.

The square root of 21019770 is about 4584.7322713546. The cubic root of 21019770 is about 275.9789681516.

The spelling of 21019770 in words is "twenty-one million, nineteen thousand, seven hundred seventy".