20406742640 has 80 divisors (see below), whose sum is σ = 50442896448. Its totient is φ = 7660443648.

The previous prime is 20406742621. The next prime is 20406742669. The reversal of 20406742640 is 4624760402.

It is a tau number, because it is divible by the number of its divisors (80).

It is a self number, because there is not a number n which added to its sum of digits gives 20406742640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7109 + ... + 202148.

Almost surely, 2^20406742640 is an apocalyptic number.

20406742640 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 20406742640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25221448224).

20406742640 is an abundant number, since it is smaller than the sum of its proper divisors (30036153808).

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

20406742640 is a wasteful number, since it uses less digits than its factorization.

20406742640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209346 (or 209340 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 35.

The spelling of 20406742640 in words is "twenty billion, four hundred six million, seven hundred forty-two thousand, six hundred forty".