645021481 has 32 divisors (see below), whose sum is σ = 757312640. Its totient is φ = 544195584.

The previous prime is 645021473. The next prime is 645021521. The reversal of 645021481 is 184120546.

It is a 12-Lehmer number, since φ(645021481) divides (645021481-1)¹².

It is a cyclic number.

It is not a de Polignac number, because 645021481 - 2³ = 645021473 is a prime.

It is a super-2 number, since 2×645021481² = 832105421902866722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (645021401) 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, 1489441 + ... + 1489873.

It is an arithmetic number, because the mean of its divisors is an integer number (23666020).

Almost surely, 2^645021481 is an apocalyptic number.

It is an amenable number.

645021481 is a deficient number, since it is larger than the sum of its proper divisors (112291159).

645021481 is a wasteful number, since it uses less digits than its factorization.

645021481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665.

The product of its (nonzero) digits is 7680, while the sum is 31.

The square root of 645021481 is about 25397.2731016540. The cubic root of 645021481 is about 864.0218513171.

The spelling of 645021481 in words is "six hundred forty-five million, twenty-one thousand, four hundred eighty-one".