21720821026 has 8 divisors (see below), whose sum is σ = 33632239104. Its totient is φ = 10510074660.

The previous prime is 21720821021. The next prime is 21720821027. The reversal of 21720821026 is 62012802712.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is not an unprimeable number, because it can be changed into a prime (21720821021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 175167850 + ... + 175167973.

It is an arithmetic number, because the mean of its divisors is an integer number (4204029888).

Almost surely, 2^21720821026 is an apocalyptic number.

21720821026 is a deficient number, since it is larger than the sum of its proper divisors (11911418078).

21720821026 is a wasteful number, since it uses less digits than its factorization.

21720821026 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350335856.

The product of its (nonzero) digits is 5376, while the sum is 31.

The spelling of 21720821026 in words is "twenty-one billion, seven hundred twenty million, eight hundred twenty-one thousand, twenty-six".