21553057820 has 24 divisors (see below), whose sum is σ = 51727339104. Its totient is φ = 7389619776.

The previous prime is 21553057789. The next prime is 21553057831. The reversal of 21553057820 is 2875035512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 76975067 + ... + 76975346.

It is an arithmetic number, because the mean of its divisors is an integer number (2155305796).

Almost surely, 2^21553057820 is an apocalyptic number.

21553057820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21553057820 is an abundant number, since it is smaller than the sum of its proper divisors (30174281284).

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

21553057820 is a wasteful number, since it uses less digits than its factorization.

21553057820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153950429 (or 153950427 counting only the distinct ones).

The product of its (nonzero) digits is 84000, while the sum is 38.

The spelling of 21553057820 in words is "twenty-one billion, five hundred fifty-three million, fifty-seven thousand, eight hundred twenty".