155921220 has 384 divisors, whose sum is σ = 632217600. Its totient is φ = 30979584.

The previous prime is 155921203. The next prime is 155921221. The reversal of 155921220 is 22129551.

It is a super-2 number, since 2×155921220² = 48622853692576800, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155921221) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 933577 + ... + 933743.

It is an arithmetic number, because the mean of its divisors is an integer number (1646400).

Almost surely, 2^155921220 is an apocalyptic number.

155921220 is a gapful number since it is divisible by the number (10) 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 155921220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (316108800).

155921220 is an abundant number, since it is smaller than the sum of its proper divisors (476296380).

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

155921220 is a wasteful number, since it uses less digits than its factorization.

155921220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224 (or 216 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 27.

The square root of 155921220 is about 12486.8418745494. The cubic root of 155921220 is about 538.2306285382.

The spelling of 155921220 in words is "one hundred fifty-five million, nine hundred twenty-one thousand, two hundred twenty".