61691220 has 120 divisors (see below), whose sum is σ = 195819624. Its totient is φ = 16257024.

The previous prime is 61691219. The next prime is 61691239. The reversal of 61691220 is 2219616.

It can be written as a sum of positive squares in 4 ways, for example, as 944784 + 60746436 = 972^2 + 7794^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 182892 + ... + 183228.

Almost surely, 2^61691220 is an apocalyptic number.

61691220 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 61691220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (97909812).

61691220 is an abundant number, since it is smaller than the sum of its proper divisors (134128404).

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

61691220 is a wasteful number, since it uses less digits than its factorization.

61691220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 471 (or 460 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 61691220 is about 7854.3758504416. The cubic root of 61691220 is about 395.1310145969.

The spelling of 61691220 in words is "sixty-one million, six hundred ninety-one thousand, two hundred twenty".