81421769025 has 135 divisors (see below), whose sum is σ = 160645656171. Its totient is φ = 40760962560.

The previous prime is 81421769017. The next prime is 81421769047. The reversal of 81421769025 is 52096712418.

The square root of 81421769025 is 285345.

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 25070605569 + 56351163456 = 158337^2 + 237384^2 .

It is a tau number, because it is divible by the number of its divisors (135).

It is not a de Polignac number, because 81421769025 - 2³ = 81421769017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 218288739 + ... + 218289111.

Almost surely, 2^81421769025 is an apocalyptic number.

81421769025 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81421769025 is the 285345-th square number.

81421769025 is the 142673-rd centered octagonal number.

It is an amenable number.

81421769025 is a deficient number, since it is larger than the sum of its proper divisors (79223887146).

81421769025 is an equidigital number, since it uses as much as digits as its factorization.

81421769025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 802 (or 398 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 45.

The spelling of 81421769025 in words is "eighty-one billion, four hundred twenty-one million, seven hundred sixty-nine thousand, twenty-five".