21749198540 has 96 divisors (see below), whose sum is σ = 51623308800. Its totient is φ = 7647575040.

The previous prime is 21749198533. The next prime is 21749198543. The reversal of 21749198540 is 4589194712.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21749198543) 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, 434951 + ... + 482369.

It is an arithmetic number, because the mean of its divisors is an integer number (537742800).

Almost surely, 2^21749198540 is an apocalyptic number.

21749198540 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 21749198540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25811654400).

21749198540 is an abundant number, since it is smaller than the sum of its proper divisors (29874110260).

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

21749198540 is a wasteful number, since it uses less digits than its factorization.

21749198540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47535 (or 47533 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 50.

The spelling of 21749198540 in words is "twenty-one billion, seven hundred forty-nine million, one hundred ninety-eight thousand, five hundred forty".