61521540 has 48 divisors (see below), whose sum is σ = 173057472. Its totient is φ = 16329856.

The previous prime is 61521533. The next prime is 61521541. The reversal of 61521540 is 4512516.

It is a self number, because there is not a number n which added to its sum of digits gives 61521540.

It is not an unprimeable number, because it can be changed into a prime (61521541) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11362 + ... + 15878.

It is an arithmetic number, because the mean of its divisors is an integer number (3605364).

Almost surely, 2^61521540 is an apocalyptic number.

61521540 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

61521540 is an abundant number, since it is smaller than the sum of its proper divisors (111535932).

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

61521540 is a wasteful number, since it uses less digits than its factorization.

61521540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4756 (or 4754 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 61521540 is about 7843.5667906890. The cubic root of 61521540 is about 394.7684163001.

It can be divided in two parts, 615 and 21540, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 61521540 in words is "sixty-one million, five hundred twenty-one thousand, five hundred forty".