21006154225 has 81 divisors (see below), whose sum is σ = 31367905923. Its totient is φ = 13913760000.

The previous prime is 21006154133. The next prime is 21006154237. The reversal of 21006154225 is 52245160012.

The square root of 21006154225 is 144935.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 13 ways, for example, as 12998052081 + 8008102144 = 114009^2 + 89488^2 .

It is not a de Polignac number, because 21006154225 - 2¹⁷ = 21006023153 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21006154193 and 21006154202.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 207981675 + ... + 207981775.

Almost surely, 2^21006154225 is an apocalyptic number.

21006154225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21006154225 is the 144935-th square number.

21006154225 is the 72468-th centered octagonal number.

It is an amenable number.

21006154225 is a deficient number, since it is larger than the sum of its proper divisors (10361751698).

21006154225 is an equidigital number, since it uses as much as digits as its factorization.

21006154225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 308 (or 154 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 28.

The spelling of 21006154225 in words is "twenty-one billion, six million, one hundred fifty-four thousand, two hundred twenty-five".