20615666400 has 720 divisors, whose sum is σ = 87840377856. Its totient is φ = 4607124480.

The previous prime is 20615666381. The next prime is 20615666411. The reversal of 20615666400 is 466651602.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (720).

It is a super-2 number, since 2×20615666400² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 21318717 + ... + 21319683.

Almost surely, 2^20615666400 is an apocalyptic number.

20615666400 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 20615666400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43920188928).

20615666400 is an abundant number, since it is smaller than the sum of its proper divisors (67224711456).

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

20615666400 is a wasteful number, since it uses less digits than its factorization.

20615666400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1053 (or 1031 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The spelling of 20615666400 in words is "twenty billion, six hundred fifteen million, six hundred sixty-six thousand, four hundred".