20978790 has 64 divisors (see below), whose sum is σ = 57908736. Its totient is φ = 4764672.

The previous prime is 20978773. The next prime is 20978791. The reversal of 20978790 is 9787902.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20978791) 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, 59254 + ... + 59606.

It is an arithmetic number, because the mean of its divisors is an integer number (904824).

Almost surely, 2^20978790 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20978790, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28954368).

20978790 is an abundant number, since it is smaller than the sum of its proper divisors (36929946).

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

20978790 is a wasteful number, since it uses less digits than its factorization.

20978790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 653.

The product of its (nonzero) digits is 63504, while the sum is 42.

The square root of 20978790 is about 4580.2609095989. The cubic root of 20978790 is about 275.7995025691.

The spelling of 20978790 in words is "twenty million, nine hundred seventy-eight thousand, seven hundred ninety".